To be honest, even though this topic has been done to death, this OP brought it up in a tasteful, respectful manner and therefore I think it could be discussed again among those who wish to discuss it.
I also agree with the poster who wrote that it might just be the type of ladies or the type of advertising places, the OP is looking for.
On the other hand, more and more ladies are speaking out and placing these race restrictions. Much more so then even 5 years ago. So this topic will come up more and more. Part of the reason is because 5 years ago, you would just screen against it. Quite often if a woman heard an accent, she would politely answer the questions but be booked when you were ready to book her. It was her way of ensuring she didn't see that "race" and you would never know. For those born here with no accent, you would get in, but quite often got shitty service. So I think knowing ahead of time is better suited you and your wallet.
As for the reasons why - they vary. Some have really good legit reasons that are not stereo-typical or racist. Other - not so much.
However it does go to show that that just because you have the green does not mean you have to be seen. These are women, it is their body and so they have the ultimate say. As it should be. Does it suck for some of you, it does. I agree hands down, but that could be said about simply having to pay for it all as well.