I would also like to note a simple fact: I doubt most men would be comfortable showing up somewhere and there is a nude man, and I doubt most women would feel comfortable going somewhere where there was a topless woman.
It is not entirely based on sex drive by any means but is rather based on simple ideas of decency.
I'm afraid I have to disagree here. "Decency" is entirely a cultural concept (as opposed to a "universal" concept). Not so long ago a view of a woman's ankle--let alone calf or knee--was considered "too much" for a (Western) man's peace of mind. Elsewhere there are Pacific and African cultures where both men and women go all but naked and cultures where a woman cannot show more than her eyes if she wishes to be considerd a decent, chaste woman.
Coming from an old and strong (unisex) sauna culture, if you like, I don't feel uncomfortable at all being naked among other women or seeing naked women, especially in a sauna/spa/lockerroom environment. I mean, I (*we*) do it all the time. So my fellow ladies have breasts of every shape and size; I have a pair too. My fellow ladies also have noses of every shape & size; and so do I. Big deal. Same with the men.
Saunailta/
sauna evening is an important and hugely popular social male/female/family/workplace/business bonding get-together event here. I have bathed with family members and friends of the opposite sex without getting all hot & bothered. Like
Kermit said, you get used to it and the "wow" factor wears off faster than you know. Of course, it helps that Finnish sauna and sex do not belong together; trying to make sexual advances in a Finnish sauna is considered a big no-no. As to the complete strangers, I have taken unisex steam baths in a quality spa and had no problems there either. It's all about the right time and place. And social norms/mores, I suppose
I suppose I could also put forward the argument that sometimes less is actually more and a body in sexy underwear/clothing can be viewed to be more desirable than a wholly unclothed body with all its flaws, if you like, fully in view.
One could explain the differences of men and womens sexual desires and how men are very turned on by the chest, and I suppose you could say that their sex drive is more piqued by a shirtless woman than a woman is by a shirtless man.
I'm sure going to regret this but, uh-oh, no, not necessarily. Me, I like shirtless male chests. A lot.