There are lots of things that are intended for one purpose but end up having alternate purposes that overshadow the original purpose.
Sexual arousal has lots of components. For men, visual stimuli figure prominently. For women - well, if anyone figures out the formula, please let me know. But for everyone, one big factor is status. Clothing can signal status, availability, wealth, and just the general ability to put yourself together. So that’s one way that clothing can be sexier than nakedness. It communicates information about you, and some of that information is sexy.
I will say that I definitely agree that concealing attributes can definitely be useful. Ages ago, when I was at a mixed-sex military training course for 3 months, uniforms were required, cosmetics were skipped, we were basically all humans in green sacks. So my baseline for getting to know the women was just as-is, as people in unflattering clothes, in an unadorned uncosmetized state.
Then in the last weeks of the course, we were given some liberty. The women put on some nice civvies and a bit of makeup. Since I had never seen their features accentuated in any way, and I had gotten to know them as whole people, the transformation was mind-blowing. Everyone was young and fit, so that helped, but this was otherwise just an assortment of average people who suddenly looked amazing. So I would definitely agree with the idea that there’s some advantage in not showing all of one’s cards up-front, so to speak.
I guess they’re no longer a thing, but a few decades ago, a lot of college towns had hot tub rental places where you could rent a tub for an hour or two. Some were enclosed but open to the sky, while others were completely indoors. Naturally, they were popular with the college crowd, and I went to my share with the GF of the moment. After a while, though, I started to think about the water, and how nearly every tub foamed when the jets were going. Then I realized how much we were adding to the soup. Once that bell rang in my head, I never went to another tub rental place again.
Well, it’s not purely cultural. Evolution clearly plays a role. Not in equal amounts and for all people at all times, but I think it’s clear that optimal attractiveness is somewhere between stick-thin (which suggests disease or lack of food-gathering ability) and morbidly obese (which suggests that maybe they can’t escape from a predator very well). These perceptions don’t just disappear overnight.
And the same goes for lots of other things, like height and skin quality. There is undoubtedly a cultural component, along with a high degree of variation, but it’s not completely arbitrary.
There are also at least two different cultural aspects. First are the arbitrary social norms that seem to drift randomly. But less arbitrary are those that result from cultural circumstances. In a civilization where food is scarce, greater weight might be preferred as a sign of wealth. But in the west, greater weight is a sign of poverty–of someone that can only afford junk food and doesn’t have the time to exercise. And this may increase in the future if only some people can afford GLP-1 inhibitors (or maybe not, if they get cheap instead…).
For some populations, it is. In the US, obesity is fairly consistent among men and Hispanics across income ranges, but strongly seen in female vs male populations:
The correlation doesn’t have to be universal to drive the perception, as long as it’s still common. Cultural beliefs can be downstream of reality but aren’t going to map 1:1.
Still, pretty interesting that the obesity/income curve is flat for men but dramatic for women. There’s probably something to the observation that low-income men have more physically demanding jobs.