They do because that is the only time we even look at them. It’s a matter of concern over the soundness of their reasoning powers. Otherwise they would be ignored completely.
Democrats have no such lock on the Asian vote (which encompasses as many different cultures as the “Hispanic” vote) but there have been no set asides or preferential treatment.
There ARE black conservatives out there. And I am not talking about wealthy black citizens, I’m talking about church going people. The Democrats get miffed when they do not vote for the leading lib (either voting Republican or staying home), proclaiming that they vote against their own financial interest and vote against civil rights for homosexuals because of religious superstition.
The coalition of special interest groups courted by the DNC do not share a common ideology, goals, or principles. There is intimidation and discrimination used to pressure people to vote for The Party or else be considered a race traitor, politically incorrect, etc.