Ebooks where such an exciting prospect when they came out, but whether it's because of anti consumer monopolies, focus on DRM protection instead of features, or

Ebooks where such an exciting prospect when they came out, but whether it's because of anti consumer monopolies, focus on DRM protection instead of features, or just plain old inertia, they haven't really advanced at all passed their first ever implementation. I sometimes read interactive fiction, and even a format as intentionally simple as Twine supports variables so content can be dynamic. There's no reason ebooks couldn't do things like that, but they are so far behind that they haven't even caught up with where print publishing was 50 years ago yet.