However I agree with you at a higher level. Our computer "file" systems have not evolved. And now they are being displaced by hundreds of isolated apps the manage out content. e.g. You might own the Jungle Book in your Nook account, but your copy of Peter Pan is on Amazon. Worse still, you don't even own these books anymore, they are instead a lease, which can be revoked at any time.
Ownership and portability of a book is one thing that becomes relevant when price includes mark up to be paid to own it.
What's different about the stream of bits on a disk that represents a "book" compared to the stream of bits that represents a "file"?
I'm pretty sure that old-school publishers and authors kept (paper) files of their works, too.
