It's not about the digitalness, it's about the hardware that enforces the rights management. You can stick every Super Nintendo game ever made on to a not-very-large SD card. It's completely digital. No one anywhere can control what you do with them. It's honestly more "yours" in that form than the corresponding rather enormous pile of cartridges.

Turning things into big piles of numbers isn't what takes them from you. It's the hardware and ecosystem that limits what you can do with the numbers. The reason Amazon could delete that book isn't that the numbers were particularly deletable somehow, it's that people were using systems that let someone else control them.