I really, really wish it weren't. A lot of stupid intellectual fights in the Black debate of ideas have occurred because people won't grant someone else is right because of an ideological label. Both sides are guilty of it. I think if they just made their case to Black people directly with sound ideas we would all be the better for it.
Because, if you convince some people that correct "common sense" belongs to one ideology or another, you can convince them to accept other stuff they normally probably wouldn't.
Because they are talking to Black people in a sense but that is not their audience. The people that fund them, give them pats on the back, arrange for them to be on TV, etc. by and large aren't Black. For liberals this means the academic circles, liberal intellectuals, and various parts of the Left. For conservatives this means the large think tanks, conservative foundations, and conservative news outlets that provide syndicated column space.
They need to get the right ideas and buzzwords in for these crowds. They will tell themselves they are really "helping" general Blacks but most of them often aren't like the old school Black liberals or conservatives. DuBois, Booker T, and Garvey all went and spoke to regular Black grounds and built institutions with Blacks to help Blacks. These guys think being a thought leader, policy analyst, and writing a couple of books is all that needs to be done.