Well, ot's something private and intimate. You don't talk about your visits to the toilet with everyone, or take a shit in front of people. But you might do all of those things with people you know and feel comfprtable with
I'm glad sex isn't "out in the open", I'm quite content with it being your own business and no one else's. Without any shame attached to it, though.
Even if a majority of people don't want it out in the open, why should they enforce that sort of taboo on others? I'm not claiming that's what you're advocating, of course, but my initial post was meant to provoke the thought on just this sort of point.
The taboo is what leads to people abusing that expectation of secrecy. Humans are notoriously malevolent with their secret dealings. Humans are just horrible.