Why the recent fixation on something traumatic in the protagonists past?
I say "recent" pretty broadly, like in the last ten or twenty years or so. I've noticed is that a lot of horror/thriller defaults to being centered around some sort of traumatic event in the protagonist past, an event consistently hinted at throughout and finally shown in flashback. The first time I remember seeing it was in Peter Jacksons BRAINDEAD (1992) but back then, it wasn't as overused. On the other hand, there were also Gremlins (1984) which played it for laugh, suggesting that it was a bit old back them.
Personally I'm a bit tired of the trope. What is the appeal? Why did it gain such popularity?