I've always found this trope strange. My friend fucked around and found out so now I'm mad about it and I'm gonna fuck around too. Like for one your friend started it, and two after you saw what Batman did to him you want some of that too?
I never really quite got it either but I guess it's one helluva way to create more punch fodder. But at this point I think people are running out of creative ways to make new characters we just need someone to breathe more life into new characters, that aren't like oh you didn't know they were actually here the whole time but in the background?