Screenplays Are Source Code
Writing is foundational, at least in the fields I'm interested in. Programming is writing where the audience is a compiler. Screenwriting is the source code for filmmaking. Neither writing is interesting in its own right. They both require additional processing to create something usable by the intended audience.
Nobody (outside of Hollywood) stands around the water cooler regaling coworkers about the great script he read over the weekend. Nor will you find hush reverence for C++ code from an end user. These types of writing are not end products in themselves but provide the basis for creating them. As such, the writing is far less fun than say writing a short story.
Short stories and other narratives are entertaining to write. A clever turn of phrase or the snarled description of inner turmoil can be a treat to create. You can show your paragraph (or sentence, even) to someone else and get a valuable reaction. Not so with source code or screenplays. Screenplays are all visuals, dense and terse. Source code, likewise, is all business.
Get too clever with either and you lose your audience.