Why is folklore almost always about fear ?

I've been checking folklore stories from different cultures including my own in preparation for the "Folklore" theme (I'm trying to come up with ideas for all themes), and it seems almost all of those stories have somthing to do with fear [ghosts, crazy murderers, mosters...] I mean think about some folklore in your country, chances are it's probably some kind of figure that you don't want to encounter. why is this the case ? and why I never noticed this before ?