Here's the thing. AC/DC, Def Leppard, Metallica, all great bands. But that's classic rock or "Dad rock" as I've heard plenty of people call it. The demographic of 18-50 year old men that listen to that, are already watching because they're in the target demographic of NFL football. That's why they've had pop singers the past few years, because they're aiming at the younger female demographic, who might not have an interest in the Super Bowl otherwise.