answered:
To wear it rarely?
You seem to be suggesting that something which has occasional use is worthless, which is the same as suggesting rarely equates to never. That is not logical.
The point of fashion can certainly be discussed, but it’s not frequency which determines its merits. Though ironically, the infrequency of its use is often part of the purpose, as I understand it.
I’m hardly an expert on fashion but I’ve been around that environment on several occasions, and of course read about it, and my understanding is that ponies wear dresses and such because they think they look good (or they think others will think they look good), or to look a bit different for a special occasion.