When you watch films and visit museums where you can see antique statues and paintings, you could notice that the men are always nude in those representations.
To explain better my thought: the pictures of different kind representing Romans have the men always weared with something. They are nude only if the statue or picture is a copy of Greek original.
The Greeks, in different actions like sport, battle, feast, are nude.
Now, the most sources tell that the artists (painters etc) were very precise to paint a person. In fact, if you look at the faces of the sculptures with attention, they are different. So, the artists wanted to paint the reality.
And in this reality women are weared but men are nude. Why? The weather?
If we take the modern African etc tribes, they do not think much about wearing both, men and women. And the Greeks had these strange difference.
Now, when I was in Paestum a week ago, it seems to me, I found the explanation. Here is a photo of one of the vases and, as you can see, the men, clearly the head there, is completely weared.
Wow, I found the solution!!!