There are too many black people in the hall to play the race card. :)

Maybe it is because of association as you said.

but she does seem more R&B to me, not "rock enough"

I wouldnt vote for joni mitchel or james taylor either for the same reason. It's hard to see Taylor or Michell as a rock and roll.

but kahn will get in eventually.

Her talent is widely acclaimed.

What is rock is hard to define. Why do i think Tina Turner is as rock and roll as you can get? Its all subjective opinion. But I think chaka kahn will get there at some point.