The cover/spine out is a marketing thing by the publisher. Cover out sells a lot more books, so the publisher will insist on certain books being displayed like

The cover/spine out is a marketing thing by the publisher. Cover out sells a lot more books, so the publisher will insist on certain books being displayed like this, or prominently on 'new book' stands. Sometimes the publishers pay for this service, but more often it's blackmail - "put our new diet book cover out or you will get the next Harry Potter book a week later than Amazon"