Yeah, I'm aware of the Sony case. And there was also often copy protection on commercial VHS tapes. AFAIK, nothing similar happened with music pre-P2P sharing although RIAA never actually condoned it.

I expect part of the reason is that the genie was already so far out of the bottle with cassette tape (and even reel-to-reel) that even they probably felt that it was pointless at that point to fight. However, a number of countries did impose a fee on blank media: http://en.wikipedia.org/wiki/Private_copying_levy