It's because of the artificial scarcity caused by the copyright laws. Now, with cheap digital distribution, that's changed a lot, even though you can't (legall

It's because of the artificial scarcity caused by the copyright laws. Now, with cheap digital distribution, that's changed a lot, even though you can't (legally) copy music and pass it around in most places. So it's going back to performances being the place for musicians to make money: the recorded music is how they advertise mostly, and then they make their real money by getting out on the road and performing in front of big crowds.