I think you know the potential audience of video games. No surprise that the most modders are of the same age/six too.
Some modders make them just because they want, others cater for users so making such mods is the easiest way to get attention/votes/endorsemants/comments etc.
Don't like - don't use. Not a problem.
Hey, there's tons of kinky clothing for guys out there too!
Anyways, I think a lot of people use Oblivion and similiar games as a place to act out fantasies that aren't possible in real life. Personally, I find excessively "sixy" armor to be distracting and immersion-breaking, but I can understand the attraction.
Really, mods are the perfect venue for this kind of stuff. Many publishers release games that are packed with scantily clad females, bulky men and no in-between, which can alienate people who want to play a charcter that doesn't fit those stereotypes. Hell, most rpgs don't even let you create characters of different ethnicities, or if they do, it's just a skin texture that's slightly more tan than the others. It's nice to have a choice, and this way it isn't being forced upon others.