There's lots of discussion about whether DRM (Digital Restrictions Management) is a good thing or a bad thing. But most of the debate assumes that the idea of DRM is actually possible. In this Slashdot posting, Eustace Tilly summarized the fundamental fallacy of DRM (my emphasis added):
[DRM relies on cryptography, and] cryptography is designed so that a message from A can be read by B but not by C. With DRM, B and C are the same person. The message from A (the publisher) must be readable by B (the consumer) but not by C (the consumer).
I hope you understand now why DRM is a concept flawed in its fundamentals.
DRM would be useful. So would a perpetual motion machine. It is wishful thinking to believe that the sheer utility of a function means it is capable of being produced.