Because it shows that neither know what they are talking about. If I can HEAR it, I can copy it. And the quality can get pretty damn good depending on how the sound is captured.
The only way I can see something like that working is a robust audio watermark containing the purchasers iTunes information. Won't stop copying directly, but would theoretically allow them to go after a "source" and possibly publish revocation lists that some devices could support to suppress "pirated" music.
Of course, that would only be applicable to online stores (I assume the record companies would force other stores to toe the line on the technology) and likely could only be enforced on iDevices. It obviously could be trivially defeated by ripping the music from a CD (for that short while we still have mass-pressed anonymous, physical media), pirates buying music using throwaway store accounts, or other peoples accounts being hacked.
But, let's face it, at this point the best they can hope for is deterrence rather than outright prevention.