I blame the Green Day: Rock Band game. What a crappy band to continue the series coming off of the The Beatles: Rock Band, which was a good seller.
Seriously, there should have been a Jimi Hendrix: Rock Band or Nirvana: Rock Band. They would have sold four times the number than that pop punk Green Day craptastic game.
Furthermore, the death nail I believe is Power Gig: Rise of the Six-String, which is the culmination of many in the music industry's beef with games like Guitar Hero and Rock Band, particularly that a-hole Lars Ulrich from Metallica. It is a game and they feel as if their music is being cheapened so they have to get all arrogant and fund a game that is not even a real simulation of playing the guitar in Power Gig?
Freaking ridiculous, yet I could be wrong.