It's the new hot trend. Everyone was making mobas, now they're making open world survival games. I hope the next trend is N&B/Besiege style games, that's one genre i'll never get enough of.
You say that now...
But yeah, this is clearly a result of Day Z being such a huge hit, and we're probably still seeing games go into early access that began development around that time. I've played my fair share of Day Z, and that game can be very fun when played with others (it's absolutely miserable to play alone). While Day Z has never exactly been free of bugs, my big problem with the other survival games I've played is that they've been so incredibly buggy, bordeline unplayable at times. Rust is a good example of that.
It seems like the survival genre is still very popular on Steam, so expect that devs are still going to flood Steam with those kind of games for another couple of years at least.
edit: It's kinda strange that we haven't seen more Minecraft clones. Or is it just Minecraft being this popular monster of a game that overshadows all of its copycats, to the point that I've never even heard of them?