I'll say one more thing and then give up, because this is like talking to a brick wall. DRM does not prevent piracy. DRM only makes it difficult for honest people to use their LEGALLY PURCHASED content.
Let's say you buy a book from company x which has DRM. This book works with your current device so you think nothing of it. A year later you buy a new device and load up your books, but the book you purchased from company x uses DRM that is not compatible with the new device...so you go to the company x web site, but they have gone out of business. Company x also used a DRM scheme that was proprietary, which means NO devices are compatible with it anymore, well there go all of the books you purchased from company x. This seems far fetched, but guess what? It has happened to me twice. Businesses shut down, DRM schemes change (remember Sony's old format?), and people buy new devices. DRM turns honest people towards those sectors of the net that specialize in breaking DRM. The vast majority of people who strip DRM do so to make their books usable, not to pirate. It hinders honest people and doesn't slow pirates down AT ALL.