What is the role of the physical book? A recent podcast interview with Tracy Hickman by the estimable Mur Lafferty raised the subject of books as souvenirs. A souvenir is something that you hold to remind you of times past, of voyages taken, of friends no longer nearby, and of events you've attended. We are surrounded by these - yearbooks, paperweights, programs, pressed flowers, bits of ribbon, and badges. We also have on our bookshelf books that have been read. The purpose of these is not to be used but to serve as touchstones to memory, to remind us of what surrounded that particular piece of otherwise worthless bit of junk.
In this day of electronic publishing novels and stories are ephemeral, no more than a scattering of electrons flitting across the screen, it source some distant server, and whose ownership more represents renting than ownership. You know that you've bought and paid for this. You can clearly demonstrate ownership by displaying in on your device. You can even show the receipt from your purchase. But the only way you can "see" this is to bring it up on your device. You can't passively "see" it as you contemplate something in the quiet of your room. You can't "see" is as part of a lifelong collection on your bookshelf. You can accidentally and quickly open it to reread a favorite passage.
I think this attitude drives a significant part, estimated at 25% of the eBook market, to purchase print on demand, hardback, or trade paperback editions of things they've already read on their Kindle, iPad, Nook, or Sony reader. They won't do this for everything, but they surely will do it for something memorable and pleasurable.
They want them as a souvenir of hours lost in another world.