At least for the physical books, it took a major weather event to destroy them. For virtual goods, cloud-hosted content, and permissionware, your ability to access the works can be taken away at any time for any or no reason, temporarily or permanently.
Jailbroke my kindle to prevent updates from Amazon permanently. I download epubs (from apple and libgen) and wirelessly transfer them to my paperwhite.
It's always a good idea to backup data that is in your possession.
Hard to do with Kindle books
True, but in this case that requires stripping the DRM too.