You can say the same thing about strong public key cryptography as well - "if you can read it, you can copy it" - but that doesn't say anything about the encryp

You can say the same thing about strong public key cryptography as well - "if you can read it, you can copy it" - but that doesn't say anything about the encryption technology itself. In the case of DRM, we are not in general interested in the received material being secret to us whereas in the use of traditional public key cryptography we are. The incentives are not aligned in the case of DRM, no matter what technology is used.