It's actually all about the DRM. Dynamic textbooks in that form factor could be done using open standards, but it's Apple's locked in proprietary format that Apple is selling to textbook publishers.
Apple cares because the publishers care. Apple realizes that the customers (the students) are locked in to the schools, which are in turn locked in to the publishers, which are now locked in to Apple.
No, going DRM would be against everything that apple is. If it is going to be an apple product then they will shove DRM on it. They want to lock customers in wherever and whenever possible.