The individual class configs only need to be used if you have a bind conflict, as it won't matter what your binds for the Spy are while playing Scout, as long as they don't impede your other controls.
Generally, it's just laziness and not wanting to avoid all the binds in the other class configs.
The main difference between normal and Vintage items is that Vintage items are all the items people obtained before the Mann-conomy update. They can no longer be acquired in any way except trade. This makes them very rare. You can recognise them by their blue name only, since people could also just rename their items Vintage. Also, as pointed out in the comments, the "Vintage Tyrolean" and the "Vintage Merryweather" are renamed to "Vintage Vintage Tyrolean" and "Vintage Vintage Merryweather" respectively.
See the Mann-conomy FAQ:
Q: Why have all my items switched to "Vintage" items?
A: Some items that used to be rare will become more common when they are available for purchase. We wanted to give players this option, but still recognize people who obtained those items “the old-fashioned way” in the past. So we decided to perform a one-time conversion of all the old items into "Vintage" versions, which will never be attainable in the future. This way, those older rare items remain rare (in fact, they're even rarer, because they're limited editions now).
Basically, Valve decided that making items available for money devalued the items, since it is less impressive to buy an item then it is to craft/find it. Therefore they converted every existing item in people's inventories to Vintage items.
Since you can no longer create them (only the items converted at the update become them) Vintage items are very rare, which gives them a higher value in trade. Otherwise they are identical.
Additionally, a couple items are excluded, such as badges, promotional items (eg. Bill's Hat) and holiday items (eg. Ghastly Gibus).
Funnily enough, the Vintage item's rarity will increase over time, as people use them up in crafting.
See also: The Quality article on the Team Fortress wiki.
Best Answer
"Is it simply a matter of luck that out of all the hats in the game, they just happened to craft one of the new ones?"
"Are there any craft recipes I can use to increase my chances of getting a low craft number item?"
If the item happens to launch with a specific recipe, then of course you can use that recipe to craft it. This is generally pretty rare, however. More likely is that you can use the Fabricate Class Weapon (1 scrap, 1 class token, and 1 slot token) or Fabricate Class Headgear (4 refined metal and 1 class token) to fabricate a weapon or hat that belongs to a specific class. If all you care about is getting a low craft number, then use the class token for the class with the most weapons or hats for that update. (See the wiki for more.)
"How can I anticipate when an update is released with new items so I can be ready to launch the game to begin crafting?"
Big updates are advertised on the Official Team Fortress 2 Blog. I recommend you subscribe to their RSS feed. Alternatively, you can read the Steam Powered User Forums to stay informed.
"Is attempting to obtain low craft number items a roulette similar to crate unboxing, or is there any strategy behind it?"
Watch Steam all day (particularly in the early evening pacific time) when the update is supposed to drop, then craft like mad. You'll want to stockpile refined metal and/or craftable hats. Aside from the few tips I've given to improve your chances, the item you receive is completely random.