Suppose you "buy" a paperback book. We all know that purchase doesn't give you the right to replicate the text of the book -- probably not even as a backup copy. So if you have a house fire and the book burns, you no longer have the book you bought, and no recourse.
But paperbacks don't have to burn to be useless. Hundred year old books are generally very fragile. So granted, Stephen King doesn't have the ability to remotely wipe your paperback of The Stand, but it's not eternal.
It's a distinction without (much of) a difference, since the paperback will outlive you and probably your grandchildren, but it's not eternal, and so technically you don't own it, the same way you don't own digital copies. The time frame over which you don't own it is just longer.