I don't agree that there are implied contract limits on your use of a CD. I also don't agree that there are normally any express contract limits on your use of a CD.
The OP references a letter from a poster who got his terms mixed up. He equates copyright law with a license/contract. That's not true. There ARE copyright laws which attach to the creative work and that would limit the use, but it's not a license.
In the end, the OP's premise is flawed regarding the music on a CD having a license attached to it.
It doesn't "specifically" say that. If you read the Betamax case, it's clear that the court was looking at the intrinsic qualities of home video taping devices. Time shifting, for example, isn't really an issue with back ups, recorded music, or books. That's not to say that the Betamax case isn't very persuasive when it comes to fair use with other media, but it's not explicit that the holding in that case would apply to other media.
They are part of the Code, but courts test what the code means all the time. Example: before the Sony Betamax case, there were the statutory provisions of fair use, but it was unclear how it applied to home taping.
RE: why software and mp3s are under license (in addition to copyright protection).
All creative works fixed in a tangible medium of expression get copyright protection. But without a license, they are useless. We are able to use software and mp3s only after we COPY them to our hard drives. The act of copying is reserved for the copyright holder. Without a licensing agreement, nobody would be legally allowed to transfer the copyrighted data we acquire.
The OP references a letter from a poster who got his terms mixed up. He equates copyright law with a license/contract. That's not true. There ARE copyright laws which attach to the creative work and that would limit the use, but it's not a license.
In the end, the OP's premise is flawed regarding the music on a CD having a license attached to it.