I've never really understood the point of writing stript-based fanfiction such as this. It seems to me that a script is simply a means to an end, an intermediate step that allows a story to be transferred to the screen.
Writing scripts that will obviously never be used as such (actors reading the lines in front of an audience or cameras) seems a bit pointless.
I can understand that it is far simpler to write a story in script form rather than writing an actual piece of prose, but somehow writing scripts that will never be filmed has an air of futility about it.