1) Record labels pay to promote the music of their artists, hoping to increase the airplay of the songs on the radio, which is free. (See the "Payola" scandal of the 50's)
2) Recording music off the radio for your personal use is legal, and always has been, AFAIK.
3) Radio is a 115-year-old technology for mass dissemination of information.
4) The Internet is fundamentally the modern, superior equivalent of radio: a technology for the mass dissemination of information.
So, the recording industry, which pays for -- sometimes illegally -- its product to be disseminated to free mass market broadcast using one technology now sues its own customers for obtaining or sharing the very same product through a modern free mass market broadcast.
The activity is the same; only the technology is different. But one is promoted to the point of bribery, while the other is brutally punished.
Why does everyone maintain that payola was a problem in the 1950s?
That myth (that it only went on then and not before or since) was cooked up by ASCAP who refused to publish country, R&B, and rock and roll songs and suddenly found themselves with nothing on the charts. They said the only way that “junk” could get there was by bribing DJs.
Tommy Shaw said that Styx songs like Lady became radio mainstays because the label was paying the progamming directors in coke. Called them penguins, lay out the white lines and the suits waddle up...