This is an excellent comment - and yes, it would be somewhat remiss of me to overlook the cosplay industry that is theatre. I would say though, to some extent there is often a wider point to seeing a play. it's supposed to say something about the human experience... it's supposed to be a journey either emotional or intellectual. Cosplay, certainly the ComicCon style of cosplay isn't about that, it's about aestheticism. I think that's a shame - it's escapism without any direction. A diversion from reality rather than an answer that takes you somewhere.
For that reason, I also hate musicals :o)