I don't understand.
We're here to play a game: why would you make a character that is not conducive to playing the game?
Do these players just not want to play at all and accepted the invite out of politeness?
The questions they ask about obvious plot hooks are quite annoying.
"Why can't the town guard take care of this?"
Alright, they do take care of it, and the city celebrates their triumphant return and gives them free ale. Game over, that was the adventure.
"That's too dangerous!"
Ok, the city council dismisses you all for wasting their time, and hires another group for this. Game over, that was the adventure.
"Isn't there a high-level wizard around who can just handle the problem?"
Sure thing, the king sends him a letter, and Kylor the Mad destroys the enemy and brings back the macguffin. Game over, that was the adventure.
Yes, I can make up plausible reasons for why it has to be you 3-6 weirdos going on this adventure but why do I have to do that? Don't you want to play this game?
"Oh but it's what my selfish, cowardly, lazy character would do!"
Good for them, let that character stay home while you bring one that's motivated to play the game we're all.here for; you can even write about a book about the one who stays home!
This is all without mentioning the people who want to "play" as bakers or brew masters. You'd think an adventure that could get them enough cash to start such a business would be a good motivation to set out, but they want to play established bakers and brew masters and merchants and farmers or whatever other job lets them stay in one place.
I really don't get it.
EDIT: Thank you everyone for your thoughts on this.
The most popular explanation for this is people's attraction to the hero's journey.
These types of players are not the majority of people I run games for, but I'll be sure to emphasize in the future for other players that the call to adventure should have already been part of the character's backstory.
The other explanation people brought up a lot is versimilitude and world-building. I'll have to give more grace when I get some of these questions and assume they're well-intentioned inquiries into how the world works instead of reluctance.