Background could be used for a lot of things other than just tweaking dialog options. A few ideas:
-Starting money/equipment
-Who you know/have a relationship with when you get to Baldur's Gate. A criminal might already have a job from the thieves' guild. An entertainer might have a rival to face off with. An artisan might have support from their guild. This isn't something that has to impact every single dialog throughout the game, but might give you a personalized NPC/mini-quest when you get to a later stage of the game. Maybe the player can define a bit about the relationship through a dialog just before they get to the city, where someone in the party asks what sort of life they have to return to or if they miss something in particular or something like that. Something like this might go a long way towards making custom PCs feel less flat without having to address every dialog in the game.
-This game badly needs to do a better job of teaching people how to play the game. A day-in-the-life tutorial before your abduction, with flavor based on your background would help it to feel like you are inhabiting a character with a life rather than someone who was essentially born on the mindflayer vessel.
