How many times have you read something where either the protagonist or some secondary character has a really elusive or painful past? Or where even the world has a dark tinge to its history? Often. Very often, I'm sure. It's one of those things that I don't think writers can really get away from because we have this desire to work our problems out with our characters (sometimes). Or we do it so our characters have an edge to them--something that can be brought back and haunt them for eternity. Do we need it to? Bad people don't always come from bad pasts. And good people don't always come from good.
Is it even possible to have a character without some sort of issue stemming from their past? I don't know. Nor do I think that there really can be. They've got to grow from something, right? Someone being good and getting better isn't something a reader wants. I know I wouldn't want to read that. Talk about boring.
But, do the pasts always have to be painful? I don't think so. Sometimes I think writers (not saying every writer!) make their MC come from abuse or abandonment... or anything else equally unpleasant because they think that that will create more sympathy. And I'd think it's safe to say that it does. But I don't think it's the right kind.
Do we only want our MC's to be sympathized with? Shouldn't we want to have the readers connect so they can empathize?
I also think that some more amateur writers also subject their MC's to a lot of pain during the story itself--not just the past. Sometimes it's okay and they've managed to write a horrible--but amazing--story. Other times it's just so much that I'm left wondering "why???" Firm believer of "Don't kick 'em while they're down." Exception being in the climax--that's where it's supposed to be! Even then though, there is a limit.
When's the last time you read something that was a bit over the top? Did you feel bad for the MC or did you just wonder why the writer hated their character so much?