Im chinese and I know a few of my friends who have dated white girls. Thing is, they're pretty much white too, just yellow on the outside, what I like to call twinkies. Seems to me the cultural difference is a factor.
Also, speaking from what I've seen, most asian guys either dont care about their appearence or hygene at all, or over do it and end up looking like tools or meterosexual.
Alot of asian guys put white girls on a pedestal which really fcks things up. I dont know why, because I think asian girls are a lot more attractive.