Most DRM is trivially easy to fool: Just pirate. When you circumvent DRM, you are pirating, except you paid for the privilege. You probably also have a bigger risk of being caught, as you still run the DRM software.
and also, while the iso/tv/movie scene has strict quality rules, the ebook "scene" seems more ad-hoc. pirated ebooks are sometimes OCR scans with tonnes of spelling mistakes or weird formatting, or ancient editions.
in short, de-DRM can still be preferable.