As a general criticism of Kindles, it will doubtless shock some users to be told you don’t actually own the books you have ‘bought’. It’s more like a long-term rental. A book lasts until the pages fall out, and even then, with care, can still be used, sold, given away or kept forever.
Books on a Kindle only last at the behest of Kindle, until (like phones) you are forced to buy a newer model or the software, which you have no control over, fucks you. The actual ‘books’ exist in some non-tangible ether or micro-relay which you only access by the grace of Amazon. Not your belongings.