Why? Because our stupid sanctimonious pious western upbringing makes discussion of sex, kinks, or even adultery somehow wrong. If it wasn't given that judgement jealousy wouldn't happen.

Judgemental people, possession of another, is all that seems to matter to societal norms.

Go to Asia, where it is different, it is accepted and understood and not judged.

Have friendly fun when you want to. Share a gift after and move on.