There have also been cases where a customer violated Amazon's terms of service and lost access to all of their Kindle e-books. Amazon has all the power in this relationship. They can and do change the rules on us lowly peasants from time to time.
Note, there are indeed ways to download your books and import them into something like Calibre (and remove the DRM from the books). If you do some web searches (and/or search YouTube) you can probably figure it out.
My wife is big on library, and I need to, but I grew up just pirating stuff, so here we are. But she has a book club, and she'll place a request for the book, and in the event it's not yet available, she maintains the request but I get it for her. And for me personally, when I like a book or a series, I go and snag them later. I just prefer reading in Kindle anymore.