But those books can be used for 10 kids (a decade of use per book, each book stays at grade level). An iPad will not last a decade in a classroom/schoolbag/kids room.
On the other hand, schools are probably interested in being able to get updated content every year, rather than using the same book for 10 years.
In some subjects, that might not be important. In others, like science or math, it might be useful to have up-to-date information presented with the latest pedagogical techniques.
Hell, being able to update textbooks to references the latest internet memes would probably do wonders at raising entertainment value.
