The Big Ten schools would all be higher if TV revenue were included. Why isn't it?
My guess is because programs get that regardless. Just by membership alone (and let's face it, the work of others), Vandy and the Miss. schools share in the SEC's TV money. If Vanderbilt fielded a team composed of cheerleaders (and many years they have come close), they'd still be entitled to all the money the SEC shares as a conference.
I'm guessing it's the same thing with the Big Ten schools and their rankings by Forbes. I know it mentioned one of Arkansas' revenue streams was increasing ticket prices (I also know the university there has negotiated some beneficial radio and tv contracts within the state), so I guess the rankings really only dealt with each institution on its own, separate from any conference/shared money.
BTW- that list and the parameters it used didn't seem very thorough to me.