Earlier quoted context omitted.
Those people are entering into and abiding by a license agreement when they purchase the book.
No they aren't. Where's the Terms of Service for a book? What about secondhand books or books you get from the library or books you borrow from a friend? I never had a book tell me to an accept a license agreement before I could read it.
It will say something like 'all rights reserved' and that you can't reproduce any part without permission, except for limited cases.
Please go get a book off of your shelf and look, I'm begging you.
Edit - Example from Infinite Jest: https://burnsiderarebooks.cdn.bibliopolis.com/pictures/14094...