sadly today I dont think most of them do have a brain..they are soooo caught up in making an impression, that they lose sight of what that impression might be...even bad publicity is publicity (Brittney anyone?)but thank god that they do have a brain and yes the stars may have someone telling them what to wear, but in the end THEY get to decide if they want to look like a tramp or be taken serious as a singer. no one has to see thier boobs hanging out or the cheeks of their butts falling in anyone face. it is their decision.
they are hammered with the idea that they have to act "sexy" (read that "trampish") by promoters that KNOW they have to cash in on that 15 mins of fame to the point they lose sight of reality (Miley Cyrus?)
in short? they arent allowed to think for themselves in the early stages, and by the time they get "big enough" (if they ever do), the pattern is already set