most people would say "obvious troll is obvious", but i think your question is genuine...
the tall tee is a fashion thing. it also covers imperfections in your skiing and makes you look more relaxed. better than a tank top, hey?
the baggy gear is sort of the same deal but its also functional. the first pair of baggy pants i got i found so much easier to move around in. once again i think its mainly a fashion thing. i hate ridiculously oversized gear but baggy is fine.