A brief preface: if you've been trying for years to teach a topic to multiple different people, it's likely the problem isn't with your students. Teaching is actually rather difficult and it's worth learning some pedagogical techniques.
At the end of the day, there are a number of pedagogical traditions you can draw upon. Here, we will touch on three of them: mimesis, granularity, and system mastery. Before we begin, however, it's worth noting that you should confirm that they actually want to learn these topics. While classrooms have a number of positive and negative reinforcement techniques built in (loss of social status for not complying with norms, validation from grades, social expectations of learning, goal-fulfillment, etc..) hobby games do not have that same structure. Therefore, the only basis for engagement is voluntary pre-commitment. Try to differentiate "saying yes because polite" from "saying yes from general interest." Different social groups consider declining an invitation to be some level of taboo, and will therefore not decline, despite not being in the least interested.
Consider figure one by Boyd and McConville: without a common mutuality of concern and shared social experiences, there is no comprehensible explanation of the activity.
Rule-complexity is actually the least worry about teaching RPGs. Much of what forms a role-playing game is a tradition of play stretching back to the originators of the game. There are cultural expectations and touchstones that are so deeply embedded in our social tradition that they do not bear comment. Simple RPGs, by their very nature, assume more of those traditions. As a gedankenexperiment, try imagining explaining why playing "golf" is fun. "You hit the ball, then you chase the ball." There are a whole bunch of social expectations and experiences bound up in the game of Golf that are actually quite difficult to explain.
Pedagogical technique 1: Mimesis
Humans are creatures that are actually remarkably good at mimicry. We learn our first language by mimicking the sounds of our parents [citation needed] (I'm so not getting into neural-encoding of languages or anything like that here.). Therefore, review the recorded let's plays in this answer, find ones in genres that interest your group, and spend an evening listening to them and discussing.
It is critical to choose genres that your players already have experience in. It is too much to teach the common genre conventions of a given domain of fiction and other things. The point of mimesis is to expose, as novel, only the things that are the topic under discussion. Therefore, try to get favourite books of your group, and find a system that exposes the conventions of the modal genre, Avoid universal systems for now, as they load more of the cognitive work onto the players. This topic is worthy of a well specified game-recommendation question in its own right.
Once you've found the system, and found the favourite books of your group, your objective will be to game in those books. You will, effectively, be engaging in collaborative fan-fiction. This shortcut is useful: originality is great for people who understand the domain. Until then, stick close to your source material.
Again, here, the objective should be to find recorded games that match your desired system and genre. You can recommend listening to these individually, or listen communally as a group. Be prepared for very low compliance for individual assignments: very few people "like" doing homework on things that they're being socially pressured into doing [citation needed].
By listening to these games, and then by discussing these games as a group after the listen, you're not asking your putative players to act. What you're doing is building their background knowledge of the actions expected in an RPG in a zero-risk environment. In these discussions, beware confirmation bias. Ask them to explain what's happening in games to you. Figure out what they're getting and what they're not getting. Make sure to provide positive and negative feedback here: it's important to validate learned concepts as well as correcting mis-learned ideas.
Pedagogical technique 2: Granularity.
Consider the idea of Granularity Hierarchies. Consider the idea of driving. When driving a car, the first time, there are so many things to keep track of: the state of cars on the road, inputs via the front window, the side windows, the rear side windows, the rear-view mirror, the side-mirrors, road noise, the dashboard, people screaming at you to stop!, etc...
After driving for a while, all of those different "tasks" are grouped up into the task called "driving" and become mostly automatic, reducing the cognitive load of driving and allowing for new, more difficult tasks like "where am I now?" and "where am I going?"
There is a rough hierarchy of task difficulty. Mastery of basic tasks is required before advancing into moderately advanced tasks. Die-rolling has a huge number of assumptions bound up into the task, and isn't actually a very good place to start. Get a "RPG board game" to get the idea of characters working on tasks with a chance of failure. Once they have the idea of "hey, this is a 20 sided die, and I should add this number and compare against this other number." then move into simple vignettes in the chosen game system. If they all read Harry Potter, for example, maybe start with "you're trying to avoid Finch's cat while sneaking through the halls" and use that as the basis for teaching action success and failure. While I don't believe this level of granularity is normally necessary, the main reason it's not necessary is because there tend to be few new role-players in any given group, given the level of difficulty you've been reporting, it's likely worthwhile to go back to basics.
Again, make sure to verbalise your own mental procceses when running your side of the screen. "I'm doing this because of this, that, and the other thing. I'm offering you Y, because you did X." By chunking the rules into small chunks, you can test mastery of those chunks before "zooming out" and playing the game.
Pedagogical technique 3: System mastery
At the end of the day, your players will have to learn the rules. Give them the books for the system you've identified, one that matches their genre expectations and one that doesn't presume on too much implicit knowledge. Then ask them to commit to reading goals before the next meeting. At the next meeting discuss what they have read and the implications on the game of that chapter.
So long as it's not pure homework, and you're using the other techniques actively at the same time, expecting them to read the books and remember the rough rules of the game is not too much to ask. It's not your job to be the book: that's the book's job. If they aren't willing to read a long book, find a shorter (but well articulated game) that does what they want. (Again, that's likely in our game-recommendation section already.)
Conclusion:
You can lead a horse to water, but you can't make them drink. Assuming your players are actually wanting to learn, the common theme is to have multiple distinct learning elements that your players can engage in. It's not your job to teach the entire social tradition of RPing. Set up a venue where they can be guided to recorded games, can practice task activities, and can get help in understanding the readings. If they don't engage, just enjoy playing board games and don't force the issue.
Best Answer
It's a measure of doing what is right. If you're losing it, you're being a villain. If you're gaining it, a righteous samurai.
As a player, you don't use it, per se. As a GM, you inform players of whether they are living up to samurai morals with it.
In combat: survive. That's it. Some may also be combat capable, but it's neither their giri (duty) nor their role. A few (Magistrates) might be combatants, but they are the exception.
Outside of combat: some are the face-men (talkers, con artists, negotiators, diplomats), some are artisans (which is good for duels of art), and some are information gatherers (magistrates, spies)
You are part of larger groups. The family (more properly, sept, a division of a clan) is a sub-clan. You have multiple duties as a samurai: To the Emperor (The Daimyō of all), To your Clan's Daimyō, your Family's Daimyō, Your local Daimyō, your wife, your parents & siblings, your family members, and your clan mates. What ranking you put those into defines, in many ways, how to play the character.
Mechanically, Clan determines what schools are available to you, and what families.
Socially, Outside your clan, you're pretty much interchangeable with any other non-daimyo non-magistrate of your clan. Only within is your personal identity valued. And likewise, unless duty demands it, you should avoid members of other clans; they are not allies, per se... except when it comes to fighting Oni. Some GM's ignore this aspect, tho'.
The Clans can, in many ways, be thought of as nations within the Union of Rokugan. They often have fought wars with each other.
Artisans are there to win duels of Art. See Way of the Courtesan for more details on that.
Geisha are non-people. They are there to entertain samurai and to be spies, and as romantic plot objects. They are not, generally, suitable as PC's. (Historically, they bordered on indentured slaves.)
The big archetypes of the Samurai Genre...
The Bushi's Bushi: the combat monster. Big, strong, tough, often not too bright. Honorable, but manipulated. If you phrase something as dishonorable, he won't do it; if you convince him Honor demands it, you won't stop him without killing him. High earth ring, high willpower.
The Thinking Bushi: A less combat-capable bushi, but still quite lethal, he tends to avoid combats, but can hold his own. Experienced bushi of this type are often excellent captains and generals.
The sneaky bushi: not a skulker and hider, but a political creature. gets others to do his handiwork. Often a courtier, but not always.
The Yojimbo: the devoted bodyguard. Once assigned a charge, nothing, not even his own dishonor, will cause him to willingly let harm befall his charge. Often, this also involves thwarting the will of the charge...
The Wise Warrior Monk: dispenser of advice and, when needed, but-kicking. Often possessed of quite the temper, but it's long, slow, and when riled, unstoppable. Usually a retired samurai.
The Silly Monk: usually a young monk, who does stupid things, but learns from the experiences. Often comic relief, and often shares bits of wisdom without realizing it.
The quiet master of the Monastery: ancient, withered, and wise beyond reason. Not usually suitable for PC's. Basically, a living encyclopedia, but also one which, being retired samurai, is capable of delivery of rather surprising violence when absolutely needed.
The Magistrate: Tasked to keep the peace, and to investigate crimes. Half courtier, half warrior, and half spy... Subtypes include the Honest Magistrate (often played the fool), the detective (who has to then coerce confessions and witnesses), and the slayer (who figures out the guilty, then kills them while they "resist arrest").
The Geisha: usually a love interest. Always duplicitous in some way. And one who falls in love with her is doomed. Not samurai.
The Rōnin: Masterless, and honorless, he's either to be pitied, abused, or paid to be sacrificed in battle. The best are incredible, but often treachery or cowardice is how a Rōnin makes it to old age.
The Shinobu: the spy, the assassin. Hides in plain sight, pretending to be one of the above, or a servant of one of the above. Usually killed when exposed.
Fantasy Samurai Archetypes
The Shugenja: Healer, priest and wizard. Makes children nervous, and worries bushi. Unless, of course, he's YOUR clan's Shugenja. Then he just creeps you out until he blasts the goo out of that there oni, or glues you back together after a battle.
The Chanbara Monk: The guy making the 20m leaps and throwing monsters. Physics went out the window when he entered the room. Naruto, were he not a ninja. In game, there have been a few schools that can support this.
Demon Hunters: usually in the game, these are magistrates or members of the Crab Clan. In the broader samurai literature, they are often monks or priests, often madmen.