Why Are White Men Singing Less?

Pivoting off the above video, Doctor Science finds data suggesting that white males are singing an increasingly small percentage of chart-topping songs. She wonders why this is:

There's a paradox here, it seems to me. The majority of top-25 hits in recent years are one variety or another of hip-hop, very broadly speaking. I assume that young white males are still a huge segment of the music market, though I can't find specific figures. Logically, then, I'd expect white guys to be buying a lot of hip-hop, as everyone else does. So why aren't they *singing* it? Why would white guys prefer not to hear white male voices? Or is it a supply problem, such that white guys who try to make a career of music have fundamentally different tastes than the much larger group of white males who *buy* music? Or has music become something that isn't considered cool or worthwhile for white boys to do for a career? That's really hard for me to believe, frankly.