You can't get a book published these days, no matter how good, unless you're already known on the national stage - corrupt politician, whistle blower, axe murderer, etc. The publishers want to see their money turn around in a ridiculously short time - like a week or two from when it hits the stands. I imagine selling a movie concept is similar - you have to pack the theatre on the opening night based on the buzz, and not risk anything on the quality of the movie ie. long term sustainability. Hence, offering a rehash of a known plot will get people in the seats, and their job is done.