Interesting question. As usual, I’m not sure that I have the answer, but that never stops anyone on the internet from expressing an opinion, so here goes:
My best guess at the reason why white rappers often fail to gain respect musically and commercially, despite the bulk of rap’s consumer base being white is the issue of authenticity.
Rap (like many of its American musical forerunners, such as Jazz and Rock - whatever that means anymore) is essentially a Black genre of music. In its infancy, rap made overtures to the mainstream (Sugarhill Gang, ‘Walk This Way’ and Jody Watley’s ‘Friends’, amongst others), but the real breakthrough happened with Gangsta rap (N.W.A. to be specific). I imagine that the White teenagers of that era were drawn to the music because it represented risk and rebellion - basically something different from what their parents were used to. So my theory is that White kids fucked with rap because it was different in every way imaginable. White rappers look the like White consumers - there’s something to be said for being able to relate to an artist on that level, but issues of authenticity and exploitation (cough, Elvis, cough) arise once you start to remember that rap is a distinctly Black artform with subject matter that often broached subjects that these consumers are accustomed to getting from Black rappers AND a number of other musical genres (see above) got jacked in the past. I hate to generalize, but the kind of White person that really fucks with rap on a genuine level is also the kind of White person that is aware of American musical history and may also be the kind of White person that harbors some liberal guilt. I dunno.
Add that to Vanilla Ice showing up with his fraudulent existence and squandering the White rapper goodwill reservoir for about a decade (until Eminem, who by the way, needed a co-sign from arguably the biggest name and label in rap at the time - Dr. Dre/Interscope - he wasn’t making it without Dre. Period) and you can start to understand why White rappers have it tough.
But the real question is “why the fuck are you asking me this shit?” Fuck I sound like Justin Bieber to you? I’m extra black my friend. Go ask a white person.
Maybe I should make that a new segment around these parts. “Ask A White Person” (shoutout to Chappelle and Mooney)…