Couple of reasons:
- the guys cannot get these types of women back at home. They are pretty much out of the guys league. Talk to some ang mo women and they will always tell you that they are suprised so many hot local gals go out with god-damn ugly ang mo men.. the ones they wont touch.
- the local gals will let them do what they want, anal, internet pictures, group sex... you think the ang mo woman will let him have that?