There's also the fact that most people don't want to hear new music. You go to the bar and there's a band, it's not the original or two they slip into the set that gets people listening - it's the covers of songs people already know.

The Beatles were one of the first British bands who had mostly original music on their first album. The Stones had only one original song on theirs. This was record company policy at the time - who would buy a record of songs they didn't know?