This is an excellent article. Much of the discussion about digital vs. dead-tree books is similar to Stallman's "Right to Read" essay [1], which was published 22 years ago in 1997. As a graduate teaching assistant who has taught several introductory physics courses in an American university, I've noticed that book publishers like Pearson and MacMillan have been pushing students to buy/subscribe digital versions of their textbooks. Professors also increasingly assign homeworks online rather than make students do it on paper. This is really sad because it's really difficult to learn physics without actually doing pen-and-paper calculations. As an example, in a particular homework on vector addition, students were asked to draw the resultant vectors on some poorly-written JS based web notebook, and the students spent more time getting the thing to work instead of learning vector addition.
I can also understand why publishers push for digital subscriptions. Introductory physics textbooks have hardly changed in the past 30-40 years (I would even say they were less distracting and had better problems 30 years ago than now), and it should be obvious for the execs at Pearson and MacMillan that their business model is not going to survive unless they introduce subscription based textbooks. You really don't need anything more than an old (SI-units based) copy of Halliday & Resnick to learn introductory physics.