Something in their business model is working. And I have a hard time imagining that NPR listeners won’t watch televised news programming as a matter of principle. So where is the NPR of cable news?
To me, the reason seems dead obvious. Radio is the only delivery mechanism that you can absorb while doing something else. Driving? Check. Cooking? Check. Reading email? Check. Lingering in bed after the alarm goes off? Check. I don't have a "principle" against watching televised news. I just don't have time. You could have Ira Glass and Carl Kassell doing the Hustle surrounded by frolicking puppies and I still wouldn't make the time to sit down and watch.