@Man in the Funny Hat 's post is just too real. And sometimes, it's not just a bad DM...sometimes the players get in on the backstory-bashing too.
One time, I decided I was going to play a pacifist character. Combat is rather boring for me, and I was looking for ways to mix it up and handle it differently...a little change of pace, ya know? But I know the guys I play D&D with, and I knew I couldn't ever tell them that my character was a pacifist. I had to keep it a secret, because as soon as they found out, they would all narrow their eyes and smirk and say "oh a
pacifist, you say? Let's just see about that, shall we?" and put me into countless no-win situations until I broke character.
So I rolled up a cleric, chose the Life domain, armed myself with a mace and shield. Pretty standard cleric stuff, right? And when we were fighting non-living creatures like constructs and undead, I was happily blasting and bashing along with everyone else. But if we were fighting living creatures--especially animals and humanoids--I would only use skills and spells. I'd cast protection spells, healing spells, buffs, battlefield control spells; I'd make knowledge checks, create distractions, use the Help action, use healing kits. A cleric can always find something useful to do.
Nobody noticed until we were like, 9th level. And sure enough, every encounter thereafter was a contrived attempt to force my character to finally attack someone. Enemies would focus on my character every round, everyone in the party would stand aside and let them rush me...