<p>Colleges and professors are often in cahoots with publishers. Schools get money from the publishers to make their newest edition a required text. Look it up if you’ve never heard of it. Sometimes individual professors (who wrote the book or get a payment for “reviewing” the book but only if they make it a requirement) get money too. That is why you are seeing more and more use of online hybrid texts and “binder-ready” versions. They can’t be resold (either because they expire or they just fall apart after a semester of use). I’d say 90% of professors know that students are being scammed but can’t really do anything about it. My physics professor deliberately adjusted his scoring so that the online content (which required buying a new book or key code for a lot of money) was only worth a small fraction of the grade, because he didn’t want students spending extra money just to pass the class when they could learn just as well from the older edition of the text. Every math teacher I’ve had allowed the use of an older text. But department heads and administrators enjoy getting “incentive” from publishers.</p>