Maybe it's excitement where they had none, sympathy from their friends or another person (e.g., the bad boy/bad girl) providing confirmation of the awful person they already believe they are. Sometimes it's good to feel bad and easier to be unhappy than happy. I grew up in a household where constant fights were the norm and being with Brett helped recreate what I was no longer getting now that I was living away at school. (I probably should have gone for care packages and cookies instead, huh?) Anyway, it's up to the person in the relationship to decide whether the benefit they're getting is worth it, and for most people that answer is no.