In an interview with Keith Richards,he talked about how the Stones never set out to be an original music band.They were only going to do covers of old blues tunes....Then one night,after a Stones show in a London club,Keith and Mick sat backstage talking and having a drink with Paul McCartney,who said to them that they should start creating their own songs.If for no other reason than it was a big slice of the money pie that was going into someone else's pocket.
Awesome tidbit.