That's probably because foreign doctors don't know what they're getting into. From speaking with American doctors, many have been offered double the salary to go to rural and non-rural positions in the south and Midwest but they would not even consider it due to the racism and hate there. Can't say I blame them. I'd do the same and I'm white. Culture matters and having a culture of hate like most of rural and quite a bit of non-rural America does is extremely unappealing especially to people smart enough to become doctors.