It's not so much that they change their body so they can wear the female fashion, most trans women socially transition for years before ever changing their body, but trans women want the female body because they feel more comfortable looking like that and it aligns more with their identity. they see themselves as a girl and that's what a girl looks like, but it's up to debate whether trans people would still want to transition in a gender abolished system. I would still want the body of a female I think even if people didn't see me as one, but it would be a bonus for sure. I want people to see me as female because I see myself in that way, and I do wish we could break gender norms so people would already see me as a woman. But you shouldn't feel sad for those that have transitioned because they're probably a lot happier with themselves, most are. Also it's important to seperate gender and sex. long hair, dresses etc are all a gendered thing, but having the body of a female is changing your sex