There are professors on both sides of the fence. Many do their best to accommodate students who have different editions of a textbook, some will write textbooks for the benefit of their students (e.g. to have an updated text that covers recent developments, rather than "tweaking" a book to profit from new editions). And yes, there are those who do seek to profiteer from their students. Thankfully I only encountered on of those in my university career, and even then he had at least one redeeming quality: he was an excellent instructor.

While I agree that the cost of textbooks are a mess and that conflicts of interest should be addressed, we should also acknowledge that at least some of these people are advocates for quality education.