Everybody always wants to switch it up and see some white women. You would think a few hit young ones would pick up on this. They would make a fortune.
I think there are a number of reasons that we don't see many young Caucasian women working in the AMP segment. These are my opinions, and others might find my logic flawed.
Many of the white girls who are in the business are there because of drug habits or other confounding factors, and don't stay young or hot for very long.
Many of the ones who do end up in the flesh trade take the amateur porn route, which pays better than AMP work (per hour of work), but which is usually short-lived as they lose their "freshness".
Of course, there are plenty of Caucasians working in the high-end escort segment.
The young hot Asian women who work in AMPs are there because their lack of fluency in English and lack of assimilation into mainstream culture exclude them from job opportunities in which they could earn equivalent pay in the civilian world.
Also, to some extent I believe that young American women from millennials onward have had the whole evil patriarchy thing drilled into their heads, and servicing men's base needs is at odds with that particular meme.
Compounding that is that Asians can always retreat back to their own separate world (temporarily or permanently) without much stigma, which would not be possible for mainstream Caucasian women.