I mean can you really get away with not addressing background or backstory in a campaign? every character has a place in the world, no matter how small, and unless they literally came into existence right as the campaign started it would follow they have a history in the world.
Run an adventure path. At least the Paizo ones I've played in, the characters basically don't matter as more than bundles of statistics. Part of that might be that at this point I'm about done with PF 1E, of course.