Originally Posted by starrigger
Not that there isn't some truth to that, but it's also not entirely true. I'm speaking as someone whose brother is the coauthor of a psychology textbook now in its (I think) 5th edition. The authors, in fact, work very hard to incorporate new knowledge, and to rewrite and change emphasis on old knowledge according to feedback and what seems to work and not work.
I agree with you. I really don't think publishers are intentionally coming out with new editions of textbook IN ORDER TO make money. It's a very cynical and conspiratorial point of view. Smells suspicious to me. Perhaps there are a few cases of those but I don't think generally that is what goes on.
Indeed, textbook authors are often professors at various colleges and there is only so much writing they can crank out. Professors aren't writing machines cranking out a book every year.