From an American female perspective here, and I may be way off base...I cannot imagine a man of any ilk NOT wearing underwear under anything, given anatomical features. Go figure kilts are looser than other varieties of attire, but still... On my side, I layer to avoid friction with bifurcation. Unbifurcated, I tend to avoid knickers-but at the same time, it is personal, and I do not advertise.

This thread of conversation would be interesting if gender X chimed in and began discussing the benefits, sensibility and side effects of wearing brassieres for the varied activity of life...Wear what is appropriate to what you are doing, in other words, THEN apply personal preference.