On further reflection, I also realize that cultural differences may play a big deal.
Asian guy and white girl - in asian cultures, the girl is supposed to serve the guy. Of course, that's toned down in recent decades, but it is still prevalent. So if an asian guy's girlfriend is your more vocal, feminist white girl, they may not last long coz the asian guy is used to, uh, shall we say, more complacent girl?
At the same time, an asian girl may get sick and tired of being treated lower than she feels she should, and go for the non asian guy.
Another idea that popped in my head is the idea that a person's parents reflect their choice of mate. Asian moms (my observation) tend to spoil their kids more. So an asian guy might be looking for that same kind of special treatment from their ladies and they're not gonna get it from non asians.
While asian dads are usually more overbearing and maybe their daughters are looking for guys who are UNLIKE their dads. Since most asian guys are taught to emulate their dads... well, you do the math.