@MrItty You are right that the book is for the benefit of the student. However, at the end of the day there needs to be a synergy between the lectures and the book. They must complement each other. They must work together. If you provide students with a book that presents the material in a different way, I would think this synergy would be harder to obtain.
Your argument assumes that professors know something, anything about teaching. This is often not the case. There are no incentives for professors to teach, let alone teach well. It is a misconception that professors are teachers. In fact, they are researchers. Their tenure, peer and industry respect, ultimately their very success hinges on the quantity and quality of the research they churn out, not on the quality of their teaching.
I have taken courses where no book was used. Instead, handouts were provided. This was hard to keep track of and follow. I much prefer a book that is neatly organized.
I never considered that a person would rely on a textbook for a different style of material presentation. Perhaps that is true. Although, the library on my campus had tons of texts on all the subjects I studied in college so if one was really determined to understand something there was no shortage of resources available to do so.
My prof’s $50 book happened to be excellent. And if you didn’t think so, why not just go to the library and find a different one? You will never be able to please everyone together.
Perhaps it is different depending on what you are studying. Engineering is pretty cut and dry. You either get it or you don’t. There is very little gray area at the undergraduate level where multiple perspectives should be considered, very little that is controversial.