@syntax It is annoying. The answer is money. They make more money by renting and ensuring you cannot share your books with friends as well as getting revenue from intelligence collectors. A few stores such as https://www.orbooks.com/ allow you to buy outright without DRM rather than rent. It is often possible to remove the DRM from EPUB's with something like Calibre, but it is a hassle. I recently made https://www.ebooks.com/ refund my purchase after finding I had to use their spying app.