If you were trying to sell a product, would you want your ads to look like this product is only for WHITE people? We are a multi-racial/multi-ethnic society, and we've grown moreso for more than two centuries now, and certainly since the Civil War. As whites become a smaller and smaller percentage of the total population, this is becoming more and more obvious, and harder and harder to deny. Interracial marriage is MUCH more common today and MUCH more accepted than it was just a few years ago. We've even legalized gay marriage--thanks to the Republicans.
I know, especially at first, whenever you see four people together in an ad or a sitcom--schoolmates, 'girls night out', guys working together--one of them has to be black or Asian. It looks artificial sometimes, I know. But it's just advertisers honestly reflecting the diversity of their audience.
Now that whites are slowly losing their majority, I know a lot of people hate it, but nobody's going to stop it.