In the most recent Enterprise episode we watched, they finally got T’pol in a normal uniform. And hey, whaddayaknow, she looks a lot better than in her special pink bunny suit! Just like Counselor Troi looked better once she started wearing a normal uniform in the 6th and 7th seasons of NextGen. Dax always looked better in uniform than in casual clothing. Well, I guess the Klingon stuff was cool.
At any rate, since the style of Star Trek casual clothing sucks (at least for women – it’s either a body suit, or some horribly 80s-ish jumper thing), but the uniforms generally look decent, I don’t know why they don’t just keep them in uniform.
I suppose Seven of Nine never wore a uniform on Voyager… but not even I will complain about that ;o).