[Quoth]

Paper books need a back to hold the paper in. Naturally the blurb and price is put there. It's significant that listings of ebooks have a cover and then the blurb and price as text. Even sites selling paper books don't usually do it different. They don't want a view of the spine either. That's only for physical shelves.

I can't think why anyone wants the rear of a paper book in an ebook, though if it's for yourself you can add it and not fuss about white space. Very few paper books match phone, tablet or ereader screen aspect ratios.