I'm sure one part is the economy and people not as willing to spend money to go to a game they can see on TV...
But I think the other reason is that despite what the pro-bowl lobby says, the 1 vs. 2 national championship game has made just about every other bowl game largely irrelevant except to die-hard fans of the two schools playing. I know I could not care less about the Fiesta Bowl, Rose Bowl or the Orange Bowl and the only reason I care about the Sugar is A) because it has an SEC team in it and B) I'm going. If I weren't going, I'm not even sure it would be must-see TV for me... more of a catch a few minutes of it here and there while I am doing other things.