It's to counter the racism, biggotry, and xenophobia present in pockets of American culture.

These shitty types of people avoid or hide within large cities - everyone is typically fine in these places. But small towns can sometimes have a serious problem with this if they are too "red" (Conservative).

In short, pockets of America are very tribal. People bond over similarities, and their shared disapproval of anything different, or out of the ordinary.