How come lots of South Asian (i.e. brown) men date women of other races but not the other way around?

I have seen a lot of men from India, Bangladesh, Pakistan, Nepal Sri Lanka, etc. go out with and even marry women who are Caucasian, East Asian and African-American.However, not too many women from that region (South Asian subcontinent) are seen dating men of other races. Could it be because the women are more restricted by their culture and hence less open to dating, especially dating men from other cultural backgrounds? Or could it be that men of other races don't find South Asian women attractive, or perceive them as too conservative and hence don't want to take the trouble to date them (since they think the women might push them for commitment, etc.)?