...and didn't exactly take the advice...
OP - just quietly do your own research and try PMing some reviewers about ladies is my suggestion...
May not hear back from anyone, but certainly seems like a better bet than this approach of seeking information.

As I've been told a few times, no one knows how the decisions are made within these agencies (unless you run one I suppose so don't waste your time trying to figure it out or complain about it if you're looking to get in. That's just how it is.

I also have no idea but I would hazard two things might be contributing to their decisions:
1) They don't want to work their girls like sex slaves and
2) The want to make sure that the clients they do accept will always be able to schedule at a preferred time in most cases.

Like I said, just thinking of ways one might explain the observed behavior but I really don't know if that's the case.

In any case moaning about it is probably as useful as complaining about the weather. It is what it is and we all deal with it.