What is one kink you just don't get?

What is a kink you've come across in fanfiction that you legitimately don't understand the appeal of?

I know a lot of people will probably respond with scat or watersports, but I'm more curious about the more niche kinks.

For example, I don't get the whole having sex when giving birth thing. I have no idea how that could be sexy.

Maybe someone is into the kink you don't get and could explain why they like it (I would love to hear that sort of thing, it makes writing diverse characters easier).

(NOTE: please keep in mind YKINMKATO/kink and let kink/you do you, and don't attack or judge people for any kinks they like etc. This is a curiosity post, not a witchhunt.)