I have to ask: how much of this do you think is because of the digital format, vs how much of it is because the digital format doesn't support certain physical

I have to ask: how much of this do you think is because of the digital format, vs how much of it is because the digital format doesn't support certain physical book methods we use? The two that come to mind are post-it notes and flipping through the book. If, perhaps, I could press and hold my finger one end of a tablet to flip through it, maybe it would make them more suitable. Also, perhaps if bookmarks I made in the book were always visible at the top of the reader, it would also make it more suitable. It might even be useful to make the application present a 3d view of a real book based upon the orientation of the device. That way I could angle it to find roughly how deep within the book a bookmark is.