I have no feelings whatsoever seeing Asian (or insert any race) women dating (insert a race) guys. The right question is: why should you care about someone else's relationships if the two involved are perfectly happy with each other?
There have been a few answers already talking about "preserving culture" and such; which I cannot disagree more.
Hence, you are more likely to see Chinese, Vietnamese and Korean entrepreneurs dominating a certain niches by relying on each other.*The importance of marriage and a family in determining your self esteem. In most cases, you're a loser in Asian cultures.
The pressure to marry and have children is simply to establish a socially acceptable lifestyle and not rock the harmonious collectivist boat.
Conversely, Western cultures are individualistic- personality and uniqueness are highly encouraged.