Well, thanks for bringing up this interesting and off-beat topic. If nothing else, it shows how things can change over the years and how rigidly we can sometimes see what are essentially fads and fashions. Hair, especially.
I have recently been struck by how differently hair can been seen around the world and through the years. It can be long, it can be short, it has to be cut, it must never be cut, it must be worn long or down, it has to be worn up, it must be greased, it must be powdered, it must be wet or dry, it must be covered, etc., etc., etc. I suppose the only reason is because hair is so pliable and whatever you do with it, it doesn't hurt (not much, anyway!). That and the fact that hair is so "there," like your nose.
When I was little, it was white sidewalls, worn well oiled. That was all right because everyone had those little white linen things on the back of their sofas and easy chairs. But even then a hair style could be the mark of a rebel, even down into junior high school. I don't remember anyone wearing sideburns but Reagan make sideburns safe.
Another theory of mine, recently developed, is that it isn't exposure of skin, as in near nudity (at any age), that is bad, going on forbidden, so much as exposure of hair. Those swimsuits can get smaller but you still can't expose some of your hair. I don't suppose any girl will dare to do without shaving her underarms. Guys? Well, I don't know. Clark Gable wore a mustasche but didn't have much in the way of body hair, even to include underarm hair. However, I've not found anything written about that, not that I've search extensively.
I'm still not sure if girls are being sexualized any younger than they used to be. My first impression is that at whatever age a girl is referred to or described as feminine is when they are not so much sexualized so much as being seen as sexual beings (not sex objects exactly). I think we kid ourselves that people only become sexual at a given age, on a given day (their birthday).
But to return to the topic, it doesn't follow that shaving pubic hair is necessarily a sexual thing, any more than doing anything with the hair on your head. It is more likely to be seen that way, obviously, because it has to do with your genitals and anything to do with your genitals is wrong and forbidden except under extremely limited circumstances, nearly always established by someone else and usually a man. Such is life and I suppose some people take baths while wearing their underwear (which must be white).
We are all dying to hear when the subject of tattoos and piercing comes up. I understand that piercing may be done fairly early on these days.