The general assumption is that male clothes/accessories don't sell, so as long as that keeps getting bantered about, it will continue to be the norm. Yet there is a constant flow of requests for more male clothing, here and on other sites. Problem is a lot of the clothing available is just poorly crafted and rushed through, so no one buys it, so the vendors don't make more. Just a viscious cycle. Add to that, most of the male figures available are extremely awkward looking, including M4, and difficult to morph them into something more attractive. So the add-ons available are limited, and finding real quality among what is available is that much more difficult.

Plus females are generally easier to work with because they don't have all the muscularity and contours to deal with when building add-on content for them - from morphs to clothing - so its easier to make a plain female model more attractive with less work involved. 

*Edit:

Its also a lot more difficult to rig full body armor so that it bends and moves correctly with the body. Skimpy impractical V4 armor is easier because you don't have all the pieces covering joints that you have to figure out how to make them bend while still looking like inflexible metal, since its pretty much just slutwear with a metal sheen. Trying to build a full suit of authentic platemail however, is a much bigger challenge. And since the general notion is that it won't sell anyway, most just see it as a waste of time and energy.

 

~Shane