I think there might be a bit of truth in what Phili posits that would apply to a majority of crossdressers and I say that from the number of posts I've seen here and elsewhere on the internet as well as from direct messages I have received. (Y'all CDers have some imaginations! let me tell you.)
That was not my experience though. What I gained from wearing clothing intended for women wasn't the pleasure... an almost high, that I've heard described of the tactile sensation of wearing certain fabrics and clothing. Wearing women's clothing and trying to appear as much like a woman as I could, gave me license to explore gender in a way that I felt I couldn't while dressed as a man.
Were there times when I was aroused when wearing women's clothing and appearing as a woman?... sure. I mean I think I'm pretty cute as a girl! But I also feel better about myself and my place in the world. I feel confident, the walls I've built are no longer there, I’m more fun, easy going and I feel sexy when I appear as a woman. (just for clarity... although trans, I do not identify as a woman. I'm an enby.)
I've seen in a number of places (although not from academic sources) that suggest that sometimes a feeling of arousal can come from those affirming feelings of confidence, strength, sexiness, etc. For me those feeling don’t happen because of the clothes though. The clothes have simply been a mechanism for getting in touch with who I am.
About those "what color panties are you wearing" or "show us your nail polish!" threads... Yeah. They're kinda cringy. But if I were to go through my history of comments when I first came here I imagine there are a TON of cringy things I said as I was learning about crossdressing vernacular and culture, exploring feminine presentation, and learning more about myself.
I’m no psychologist so I'm not sure I can speak as to whether any ordinary person who is deprived of emotional and experiential deprivation would engage in fetish type behavior. Maybe? Probably not. But hey... if you're not hurting yourself or anyone else, paying all your bills and taking of your family... who am I to judge.
By the way... gray cotton hipsters with a little pink bow in front. :D
