One of my quirks is I quickly consume or devour any game system that catches my attention. I have read a lot of books and want I play all of them, but I have to face the fact that it would be impossible without giving up on life and just play. I found a simple solution and that is create characters. This lets me try the character creation and give me an opportunity to create a back story for the characters I make.
But I think the biggest reason prepare a lot of characters is option paralysis. When I try a new system the choices tend to overwhelm me because I want to try them all and during the character creation session that makes think and decide longer than is necessary, and given the limited time we usually have I don't want that to go to waste.
I usually prepare two to three characters, this allows me to make adjustments with the group. I usually get the character type that is missing. An example would be if we already have physical and social character I take the mental type. This balances everything and makes the game more fun in my opinion.
That is for now because I need to sleep.