Sometimes, rewards and incentive are motivational enough on their own. In a tabletop RPG like this where bonus exp, gold, or any other non mundane item gifted to a player for doing something that is largely required by the player as a means of character maintenance after each session and before the next is going to lead to unfair advantages when 1 or 2 of your average group of 5 end up majorly ahead in exp or currency or wealth measured in possessions (items obtained). Even Inspiration is something not to be handed out lightly.
So when rewards and incentives create imbalance? What's left is rules and regulations. My group always does their leveling at the end of each session, after XP is awarded, if said XP is enough to progress them to the next level. Sometimes our sessions run for 5 or 6 hours and everyone is too tired to do all the math and additions required for level up. No worries, they have a full 7 days to level their character! Seven days is plenty of time. There should be time in anyone's schedule over the course of 7 days to level up a character. Minds can be slippery sometimes, however, and reminders are required.
So how do you effectively go about this while respecting your players time restrictions and motivate them in the process? You make a hard rule. Session start time is Session Start Time . Character leveling up is the players responsibility. Anyone not sufficiently leveled up by the start of the next session 7 days later uses the character they have as represented on their character sheet. If they didn't go buy manacles and a chain, and the start of your session doesn't allow for shopping? If they didn't add all the nifty new things they gained for reaching level 4 and the session is starting? Well they're missing out.
You might say "Well that seems harsh, Airatome, where does the madness end!?" Well; you supplement that with reminders, if possible. Our group plays over skype so there is a consistent group chat always active. Whatever forum you use to bring your players together as a group has a method of messaging your group. So remind them at the end of each session to level up and shop. Remind them a few days later to level up and shop. Remind them the day before your next session to level up and shop. Anyone failing their responsibilities to keep their character sheet current after positive reminders and reinforcement is then stuck adhering to the rule of Session Start Time.
They can then level up their character if there's a break, or after the end of the session, and catch up to where they belong. Additionally, time allowing, you COULD have a soft session start time 1 hour before the implemented hard start time for those who need to catch up in levels and spend gold and such. This will not only give the people who already have done so time to make it to the session's actual start time, allow you as the DM to help any players who need it with their level up and HP rolls, but also allows everyone to start on an even note after the soft hour has concluded and the actual session begins. No delays. No giving out gold or items or Inspiration to those who should earn them in the game not out of the game because of a character sheet.
Regardless of the optional 'soft start time' being used, implementing a 'Hard Start Time' along with positive reminders after, in between, and a day before sessions should motivate them in a way that does not sow discord or advantages/disadvantages among the players; because after all is said and done, they DO gain the level they were missing; it's simply their responsibility, not yours, to keep their character current.
There are good things and bad things about having the players take up control of the narrative like this. I will challenge the frame slightly to suggest that "taking back control," might be less appropriate than "maintaining control of what you feel strongly about."
For instance, you might want to GM a relatively low fantasy saga (say) but the descriptions from your players veer more and more toward the high fantasy, or the four-color comic books, or some other genre. In such a case, what is important is not controlling every detail of the descriptions or the NPC actions, but enforcing the overall genre conventions.
Or you might not care too much about genre (or just might not be having that problem) but might be in a situation where you need to detail NPC actions-- even in death-- to provide some key details of the setting. If they describe a beheading and a fountain of blood for something that is actually a construct or a bloodless undead, well, that's a problem!
But the solution is not necessarily to shut the players down entirely and take back all control. An equally good method is to sit them down and make it clear that you have veto power over their descriptions, that sometimes you'll explain yourself and sometimes you won't. In the case of genre enforcement, explanations are probably warranted. Other cases are play-it-by-ear.
(And neither the initial talk nor the veto instances need to be aggressive or confrontational unless the players make it so.)
The short version of this advice is: Figure out what you really care about, and protect that. For the rest, be grateful you have engaged players.
Best Answer
It does what a tent does: provides temporary shelter from rain, snow, wind, cold, sunlight, and so on. Depending on the severity of these conditions, the lack of such shelter could create a situation where restful sleep is impossible. In the absence of restful sleep, most humanoids accumulate levels of exhaustion, which is debilitating and eventually lethal. The conditions themselves, if severe enough, could even be life-threatening (leading to hypothermia, sunstroke, etc.).