Then why even bother making them write it down and turn the whole exercise into a Flash Fiction challenge.
I find all the sniping and mockery of people who actually put some thought into their characters hugely disrespectful. Like if they spoke it out loud people here would be interrupting with BORING! I DON'T CARE, CHECK OUT THE LOSER WHO WANTS TO ROLEPLAY IN THIS ROLEPLAYING GAME.
If someone really put a huge amount of effort into their character, great, they can show it in play and have it affect the fiction. As events come up in the fiction, they can use what they wrote down to shape how they play their character and interact with the world.
I find it disrespectful to present a book to the DM and state that you expect everything in there to become part of the campaign.