The title is a little deceptive. I’m not raising this question in the hopes of finding some lofty, philosophical answer, but because the question itself is important when crafting any individual story. The question is really “why is this specific story being told” and it’s this question that writers oftentimes overlook. What is the occasions of this story’s telling? Was it an action that precipitates the story’s need for transcription. Is the protagonist writing it down themselves (in a diary, journal, what have you). Maybe a character is simply a storyteller by trade, or has to because their life depends on it, like Scheherazade in the Arabian Nights. My point is that a story can just come into existence before the reader, and they just accept it as is. However, the question of “why was this story written” still persists. What is the bias in the narration? From whose perspective are we looking through? Even if its not explicitly laid out before you in the final draft, I think its useful for the writer to consider the fact that stories have an occasion, a reason to be. Working out the details of this reason is a practice that can help reveal the complete narrative in all its storyness, which the writer can then cut down to size.