I read an article many years ago, that I can no longer find, which discussed the fear of blank videotape and how it would destroy the home-video market. Instead it created a market that was of a size unforeseen. Bottom line, digital rights management (DRM) is more of a hindrance than a protector.
Books purchased through Amazon are protected against copying and distribution by a level of digital rights management that can no longer be bypassed.
This prevents people who have purchased a digital book from reading it on non-Amazon devices.
It’s equivalent to Amazon selling you a physical book that can only be read by the glasses they provide.