I've worked in advertising, and fashion. The use of diversity in advertising started out as a way of appealing to wider markets. The use of diverse couples wasn't a decision made by an executive on a sneaky Jewish payroll or something. It was a casting director, or a creative team, or a marketing team in a meeting saying: 'We should have more diversity in this shoot.' Nobody would ever say that was a bad idea, even if 99% of the target market were indigenous western european (white). The person saying 'we should have more diversity' probably honestly believes that overrepresentation of minority demographics will solve the 'problems of whiteness' in their industry, despite being unable to identify what those problems might actually be. But why is it always black men + white or asian women? The people in advertising want their models to look attractive. Even if they're plus size, they're still casting model with attractive looking faces. A lot of attractiveness is based on amplified features of manliness or womanliness. I'm talking about jaw lines, cheek bones, foreheads, eye size and shape, etc. This isn't to say that black men are more manly looking than white men (although in many cases this is true), it's that its easier to cast a more manly looking black man than a more womanly looking black woman, because fewer black women fit the mold of attractive when measured against all races. So if they're casting an attractive couple and want to include some diversity, but casting an attractive black woman is difficult, the woman ends up being white or asian, and the man ends up being white or black. For similar reasons, but in reverse, you rarely see asian men cast in manly roles, because their biological manliness features aren't as pronounced, in general terms. In short, the stock of attractive black women models for these couple shoots is in short supply.