... it's a commentary on the quality of the general clientele.
When I book a session I spend time ensuring that it is someone I want to see, I do research, I check here, and other places for information, I search for pictures and rates, and I know if this is someone I want to see before I ever even contact her, or her scheduler.
When dealing with a scheduler you need to understand that most times the scheduler (I know a lot of you will hate to hear this, but you are probably dealing with a man more often than a woman) works for multiple ladies, gets paid for each booking, and is more than happy if the specific person you are looking for is unavailable, for whatever reason, and you book with someone else.
I call this "just looking for a nut" and so many guys do this that the schedulers would be stupid not to refer you to someone else on their list.
Personally I just say something like "Thanks, but I was looking for a specific experience" and move on.
But the "just looking for a nut" crowd, who says "OK!" and books with who ever is available is why this happens.