Probably because from Apple's perspective, all Apple did was let the publishers set their own book prices. That's basically what this case is about.
No, continue your reading and research. This is FAR from all the case is about. Apple entered into a collusion with the publishers (who have all ran for the exits) to fix the price of e-books across the entire industry, and to trash the first sale doctrine in the process by forcing every reseller to be the Agent of the publisher.
There is no way this could have been accomplished previously. Apple did this to raise margins because they wanted and demanded 30% on everything sold thru the iTunes store, but there was not 30% to be had with Amazon working on much slimmer margins. The only way this could be pulled off was for all publishers to simultaneously force all resellers to Agency terms. That required one big (new) reseller with nothing to lose, to agree to it, so that the publishers could preserve the e-book market, and force the smaller resellers to toe the line.
And while we like to blame Cook, it was really Jobs who formed this conspiracy.
But the way this lawsuit works the last to agree holds the largest bag. And Apple was too proud to admit its part in this collusion, and as a result they are going to pay up big. Very Big.