Where Is The NPR Of Cable?

This chart has been floating around:

Several bloggers have asked why no cable news show has mirrored NPR's success. Julianne Dalcanton doesn't understand the mystery:

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.