Average amateur musicians love to make music with other people, but it is really hard to do as the whole thing involves getting together physically, practicing a lot to be decent together as a band, etc
While there has been quite a few attempts at online music collaboration, clearly the average amateur musician is not using any of them.
PROs use pro-music software to collaborate with other people, and some tech-oriented amateurs hang out in collaboration forums.
But all that is too hard/annoying for the average amateur musician.
BandHub "The Internet Music Studio" - makes it easy to make music with other people over the Internet.