Its basic supply/demand imho : internet brings perhaps a tenfold increase in electro demand, but also a hundredfold (or more if you count in the likes of http://www.newgrounds.com/audio/) increase in production.
There is also that, while demand rose, I don't believe that the core group that would buy the music if they couldn't get it for free augmented that much. Those are typically the people who pay for vinyls and for live performance nowadays.