Lots of well-adjusted men find something appealing about a woman who looks a certain way. And one could quite easily ask well why don't those men like women who look a different way? Ah but the fickle beast that is human desire rarely if ever lends itself to rational explanations that would respond to your question. Perhaps we've all been conditioned to accept one form of beauty above all others (reminds me of the billboards I saw in Beijing featuring Western models in beauty product and clothing ads). Perhaps we've been predisposed to believe that a certain type of woman will be more wild and crazy than another type (porn stereotypes anyone?). Or perhaps this is one of the mysteries of the human heart and the unknowables of the amygdala.
Of course there is also the possibility that this is also a supply problem. When I look at the CItyvibe or Eros listings I would guess they're s75%+ caucasian and Asian listings. So if there are few AA providers it would stand to reason there are few reviews of them. And if providers like yourself have looked at the numbers and decided to do something else then the number goes down further and the prophecy becomes self-fulfilling.
I wish I had an answer but between the ineffable nature of the human heart and the inscrutable features of this curious hobby I'm afraid enlightenment will be hard to come by.