As far as on an individual basis It might be that some would rather do than say.
It might also be that some prefer to put those thoughts into words and are working on art right now to express it.
For those that do fit your description though, man...

these cats' reputations are carefully curated, I bet some of them are waiting to see what rap heavyweights say first (Jay, Diddy, etc) so they don't fall on the wrong side of history
And alot of them are "massa"'s bytch and don't speak unless they're given permission and briefings first
You also have to consider that these rappers don't own the media platforms they speak on. So it could be that whenever they got some anti-establishment shyt to say, the mic gets cut off so to speak... but when it's superficial/ fukk shyt, or some degrading type shyt goin on, they get a bullhorn...