Simple answer, profit, line must go up. If it makes financial sense in the future to pull shenanigans with book access or content, they will do so unreservedly

Simple answer, profit, line must go up. If it makes financial sense in the future to pull shenanigans with book access or content, they will do so unreservedly and with haste. They have done this already in small amounts, no reason to think they won't do it on a larger scale if it becomes worth their while. Steam is an interesting example, technically some of the games are DRM free (as in you don't need steam to run them) but most of them rely on steam in some form for continued usage. The main difference here is that steam has better PR and a history of not fucking everyone over for an extra % on profit margins. Will that remain the case, probably not, especially after Gabe Newell dies, but they certainly have the general trust of people who use the platform. Not to say they haven't had their share of fuck-ups over the years but none of them seemed to have "I'm a billionaire so i can do whatever the fuck i want" energy to them. That's just personal opinion though.