>Even as the big publishers work to increase the proportion of sales that come from digital products, they’re still largely dependent on physical books.
The other issue the large sum of money they want to charge per book. The cost of the books is so high that it is propping up "physical book" market. Mostly because publishers have offered no way to resell your digital or ebook. Lots of students buy used text books, and students that buy new often sell their books to recover some of the cost when they complete the class. The publishers see digital books as a way to prevent students from doing this so that everyone has to buy new (at the ridiculously high prices). The students are going to do what is economical for them, until the prices either drop significantly, or you offer an online marketplace where students can sell/trade digital books then physical college text book industry will be here to stay.