Well of course it's a fetish, for some, in some ways.
I definitely had a fetish thing going on in earlier years. It's still there, a little bit. It was mostly about close fitting clothing, underwear (obviously) sports clothing, usual things. These days, the fetish aspect has mostly retreated to the background, comfort in underwear is much more up front, womens underwear is far superior to mens, I even find the right styles fit better. I can find some very comfy mens if i go hunting, but dear god the good stuff is expensive! Much easier and cheaper to find womens ones that fit and buy on sale!
A lot, (maybe most) guys have never considered underdressing, but many have. The honest ones have realised that its superior, and the taboo aspect adds to the simple sensual pleasure of it. Whooppeeedo! It fulfils the function required, it's more comfortable, and it gets your crank turning, what's not to like?
These days I realise that part of the "thrill" is the idea that this is someting that I can do that is about sexual , physical display. Men "aren't supposed to do that" in current mainstream society. Phooee to that!
Given the level of liquid refreshment that I have taken, this post may or may not make sense.