It has everything to do with who you can name. With Beyonce comes Jay and Kanye, and despite the recent success of Mumford and Sons, they'll never hit the popularity of those two. While, granted, they're very popular and successful right now, they're insignificant when compared to Kanye and Jay in the simple fact that those two are the biggest names in hip hop over the last 5 years. The NFL is finally recognizing the demographic that watches the Super Bowl and finally putting artists out there who they can relate with, not bands that were popular in the 80's. Mumford and Sons is popular with one particular demographic while bringing Kanye, Jay and Beyonce hit the hiphop and 'pop' demographics which please the male and female viewers.