With a few notable exceptions, today musicians need to be good looking in order to be marketable. It's much easier to take a beautiful or handsome model who doesn't have musical talent and use technology to manufacture a musician out of them, than it is to take a homely but talented musician and manufacture a star out of them.
Also, they must work alone. It seems a music "artist" these days is only the face of the operation, the composers and stage musicians deserve no mention apparently.