Yeah, I agree, but it seems more and more top shelf mixers are getting projects recorded at home or in project studios. I get the feeling that a rather larger percentage of the work they do is with less than perfect tracks, stuff that never makes radio, but pays the bills. Of course, there are a couple of guys who probably have enough business from major label stuff, like CLA, etc.
That's one of the reasons I wanted to start this forum. I think working with a variety of tracks, of varying quality is a tremendous help in learning to mix. Even for someone who's been recording a long time, hearing tracks recorded by someone else can be an eye opener (for good or worse!)