There are pantsuits designed for women, but no dresses designed for men. Even further than that - a dress is very specific to female anatomy in a way that a suit isn't, to male anatomy.

The real issue, however, is that a woman wearing a suit is perceived in a certain way (as aggressive and, funnily enough, "only imitating men") while a man wearing a dress happens to be an often frequented motif in comedy.

Finally, a man can wear a dress specifically to underline just how male he is, because "even a dress can't take that manliness away".