So why wouldn't publishers just make people sign a similar agreement if it's that simple?
Would you sign a contract to get a book?
I wouldn't pay $180 for a book either, but most people who buy textbooks don't have a choice.
Even if I did sign a contract to get a book, it would be very hard to enforce conditions like not lending or selling it to somebody (unless it was an e-book with unbreakable DRM).