People choose to adopt or read a textbook because (a) it's on a topic of interest and (b) they trust the author(s) to have curated and synthesized info into a single representation (the textbook). Now, imagine this: subscribing to a curated, synthesized, online source where the author is actively, frequently updating their curation and synthesis based on new evidence. Would you pay for that? Would you adopt it (perhaps a cheaper, time-limited version) for a course?

@edutooters @psychology