Is it really? I rolled a boulder up and down a hill all day, pay me.

"Nobody asked you to do that and nothing productive was accomplished. Nobody will pay you for that."

But I worked really hard! Labor creates value, therefore I am entitled to payment.

Whether you're rolling a boulder or writing a book, your labor hasn't created value unless you've actually produced something other people subjectively believe to be valuable. The subjective theory of value is common sense. The labor theory of value is obvious bullshit. It might fool children but for an adult to believe it requires brainwashing.