Why does the great gatsby start off with nick telling his story?

The story is narrated by Nick whom is remembering what happened that summer when he went to visit his cousin Daisy and he met Gatsby

Because Nick is the narrator of the story

A. they give the reader hope. if the whole book was dark & unhopeful it’d be a little less interesting, little moments make it more interesting to read because then you want to know what happens. if it’s all dark there’s no point in reading if you already know the outcome of it.