Similar to the full app backup use-case mentioned in another comment, I regularly use root to (through adb shell) make a personal backup of my owned kindle books and keys which I can then use to convert them to DRM-free epub and read those books in non Amazon approved apps. The encrypted books are in shared storage but the key to decrypt them is in an app-private database. I also occasionally backup my own apk/obb files.

A "security model" designed around the idea that users should never be able to have any kind of access, not even read-only, to the data that app developers store on their owned device if the developer doesn't want them to is one that is fundamentally incompatible with computing freedom.

I keep a secondary device with rooted Lineage at home for the few apps I want root access to, instead of rooting my daily driver, but I always feel like it would be reassuring to have the ability to make proper backups from my main phone.