In Hollywood, there are often several writers on a screenplay. There is also a huge churn rate on a single script, where writer after writer tries to make it work. Each of them is paid tens of thousands of dollars to contribute, which is why scripts can cost hundreds of thousands and even millions of dollars. In the end usually only three of these names appear on the credits of the film.

I had a friend who worked on a film with an A list star, and in the end only one line of dialogue of his remained in the film. But he still got a credit as one of the writers! He was able to use this credit to constantly work in Hollywood for thirty years, earning over a million dollars a year writing and rewriting scripts, none of which ever got made! This is a very common story in Hollywood.