It's all about Customer Service, at the front door...
You are generally treated better at an Asian Massage Parlour, with a few exceptions if you are a Gwailo. If you make the mistake of asking for an Asian girl in a "white" parlour, you'll either be treated rudely and shown the door, or the lady will go to the back room and yell out loud: "The guy wants an Asian", and make you feel like a shithead for asking. So, the poor pooner is almost encouraged to seek AMPs, where he'll at least feel welcome.