It can be a phase too. And perhaps a necessary one. You feel isolated and rejected. You start to defend yourself - perhaps mainly against your own judgments projected out on the world, perhaps against certain value. You start to blame. Probably not a good place to stop, but it might prevent suicide for some. It might be more honest. Some people get stuck in this ‘I am so nice, why does no one like me’ attitude without any noticed anger, and that’s likely not experiencing much of yourself.
After getting more on your own side and owning some of your anger, you may be able to move on. You might even be more attractive, being a fuller version of yourself.
Note: I am not saying this is true in all cases, just that it might be in some.
I suppose it could also be part of a degeneration also. Either way it might be a phase. Like being a goth in high school, but not later.
It serves some purpose, allows one to accept oneself or certain emotions a little more, then is left behind as a more complete self is gained (hopefully). Certainly others can go to the grave in those attitudes also.