I don't think a lot of young people realise just how repressive society was when it came to sexuality. Even when I was growing up in the 80s, and from a male perspective, sex outside of marriage or cohabitation was still frowned on by many, gender and sexuality was ruthlessly policed - the worst thing you could be at my school if you were a boy was 'a poof', even long hair was a big deal, porn barely existed until videos came along and a flash of female nudity in a Hollywood movie was enough to sell a film - most of me and my friends saw our first female nipple in films like Trading Places, or in a manky old copy of Razzle we found in a bush. In this context sex was a way to rebel, and losing your virginity as young as possible was a way to gain social standing. Whilst I can't speak for women, certainly a female friend of mine who shagged people in bands a lot older than her appeared to be doing this both as a form of rebellion, and enjoyment, even if like many other vices, it could be a bit hollow and sordid.
Of course one of the upshots of sexual repression and resistance to it was that this often manifested in ways that seems very unpleasant by contemporary standards, the aforementioned Trading Places is horrifyingly misogynist, the kind of porn that got passed around after the advent of video - pretty much every boy in my school probably watched some of Animal Farm (don't google it you guessed right) - was worse than much of the readily available porn teenage boys watch now, and a lot of the music, both mainstream and alternative, was sexist crap. I guess this is what happens when a sexual revolution happens within patriarchy, the gains made in the 60s, 70s and 80s did not overthrow male dominance, what we were actually seeing was a shift in patriarchy from the denial of female sexuality to the exploitation and commodification of female sexuality. Within the space opened up by that change empowerment could be found, but it also masked a fuck of a lot of abuse.