I'm inclined to think it is generational. For young people, the pull of wanting to look like their peers is very, very strong.
Our church is mixed race. MOST of the married couples in it are interracial. There are black/white married couples, white/Asian married couples, black/Asian married couples, one other white/Native American married couple besides my husband and me, along with the pastor himself being white and married to an Asian lady. Seeing a married couple both of the same race is actually the exception, not the rule, in our congregation. Pastor says he's heard other clergy express envy that his congregation is so diverse, and wonder how they can get theirs that way. I don't know for sure that being part of an interracial marriage himself has anything to do with it, but it might.
One couple, a black man married to a white woman, has twelve children between them, sort of a "yours, mine, and ours" kind of setup. Some are black, from his prior marriage, some are white from hers, and of course theirs together are biracial. Therefore it's safe to say most of the children and youth are biracial, or the people they most closely associate with are.
And nobody at our church sags. By which I mean, deliberately belting the pants around the thighs, exposing the underwear or the posterior.
They don't generally wear suits and ties either, but that's sort of a different thing.