I hate to be an echo, but seriously, did you actually think this through. Buying the rights to any band is going to be expensive. In order to make profitable, LEGO would have to sell more sets than if they just released a generic band theme. Wouldn't it make more sense if LEGO released a generic band set that you could pretend (or modify) was your favorite band?
There are literally thousands of bands, and for almost every one of them exists people who claim that the band is their favorite. While some bands are more popular than others, that still adds up to be a lot of popular bands. If you make a AC/DC set, then you need to make Led Zepplin, then the Beatles, then Elvis, then the next thing you know, you're getting the Jonas Brothers (and nobody wants that (except for Joe, he wants that)). Have I made my point, or do I need to bring up Hanson? Let's hope for everyone's sake that I have.
The beauty of a LEGO MOC is not the elements that go into it, but the way those elements are put together.