How come band/Song XYZ isn in the game?
Lots of reasons. It’s not like HMX can just pick a song, make some charts, and give it to us. First, there’s licensing. They have to talk with record labels and bands to get the permission to use the song. Some bands are notoriously stringy or exhorbanantly expensive (Led Zepplin falls into the former, The Beatles fall into the latter), which eliminates some bands. There’s also exclusivity deals (Aerosmith and Guns and Roses might be a while). Finally, lawyers are involved in all of this, so nothing’s a done deal until you can actually pay for it (hopefully).