There are all sorts of rules and incentives for minority businesses, and a whole cottage industry has been set up.
I had a photography assignment for Hefty styrofoam dinner plates. The ads were targeted to black and Hispanics. Corporations over a certain size must use a certain percentage of minority-owned subcontractors. So there's a whole slew of minority advertising agencies that get their contracts because of those regulations.
I've found that the level of talent is much lower than at a "regular" ad agency. It's not that minorities don't have talent, but I suspect that any talented art director wouldn't want to be pigeonholed in that way, so the mediocre ones work at the minority agencies.
Absent the government regulations the agencies would probably fail because they don't know what they're doing.