A major difference being that a book reader doesn't say they're doing anything in particular with the book. People hiring creatives, though, very rarely say, "Well, we'll give you your money, but there's a 70% chance we'll fuck you over." Important other differences include exclusivity (readers aren't), amount of time wasted (after the book is published, each additional reader consumes approximately zero author time), type of relationship (readers are consumers; creative employers are collaborators), and expectations of control (which are common for creative workers).

A closer analogy is a film director being upset that the studio didn't live up to the expectations created during the deal negotiation process. That happens all the time with films, and approximately nobody tells directors, "You got paid; STFU."