I wonder (this is just conjecture) if the point for a lot of prompters is to have somewhere to share their ideas and story outlines, either to get validation or just to get them out there, and they don't much care how or even if random strangers interpret them themselves?

I mean, it might explain why there were so many long, detailed story outlines disguised as prompts being posted until the mod put a stop to it. It's a way of sharing what the prompter presumably thinks is an "amazing" idea for a story that they came up with, without having to go to the effort of actually writing it as a proper story. Basically, it's more about sharing an idea with the fandom than about getting a fill.

Just some thoughts...