There's a difference: I own the code that's on my server, but the artist does not own the music that's on my desktop; I do (logically, if not legally). If I sell software to someone, and then they want to sell copies, that's their right. I use licenses which explicitly recognize that right, but even if I didn't it should still be up to them, except where contractually barred.

If the artist wants to keep people from selling music they've produced, they're free to do so, by not selling it or giving it away. When they've sold something, however, it's not up to them to control another's actions indefinitely.

Obviously this is heavily at odds with current law where I live, but fortunately it's easy to get around said law by using licenses which give legal weight to rights a person should have with respect to easily copied materials.