The LOTR film rights is a separate issue, since that was from decades ago.
But for other films, think of it like with VC terms and startups. The best ideas can dictate their terms and get points on the gross, while the ideas in the middle have to accept a deal where they get points of profit in order to get the film made.
Somebody like Eddie Murphy can demand gross points, while a first time indie filmmaker cannot.
Tolkien's deal was signed in the 60's and Jackson did have gross points, he was also a producer of the film so he was the other side of the table. His lawsuit was much more nuanced than a straight up gross vs net calculation.
But for other films, think of it like with VC terms and startups. The best ideas can dictate their terms and get points on the gross, while the ideas in the middle have to accept a deal where they get points of profit in order to get the film made.
Somebody like Eddie Murphy can demand gross points, while a first time indie filmmaker cannot.