I don’t think that’s why. I think it’s just because it’s cheaper. My school had communal showers, but we didn’t use them (sports teams did though). The only ones I ever used were at Boy Scout camps. I’m pretty sure it’s because it used to not be considered a big deal, and it’s saves a lot of money. Honestly, I think it’s an issue it has become such a big issue. Most countries aren’t so uptight about nudity. It’s an American thing to be scared of nudity.