Inevitable betrayal trope?

Far far too many forms of media lately are all about the betrayal that the audience knows early on, but the protagonists do not.

I _hate_ this, for a few reasons:

1) there's enough horrible things happening thank you
2) much like horror movies, I am on edge the entire movie after the betrayal has been made clear that it will happen. (Horror movies are hard for me due mostly to jump scares, which are very much drawn out via music and sound)
3) I don't understand the appeal, at all.

Betrayal, fine. Knowing about it for most of the show, no.

I mean, I'm not a fan of suspecting that horrible things of any sort will happen. There are certainly instances where I want spoilers, and usually it's so that I a) know it'll turn out ok, or b) that it won't and I can stop watching. Sometimes even knowing doesn't help enough, but it can help me push through hard stuff.

But... It's really hard to avoid nowadays. I don't get it. Even watching kids' shows isn't enough.