And because writers and readers share knowledge of a big portion of this body of story, this mythology, when writers use it, we readers recognize it, sometimes to its full extent, sometimes only dimly or only because we know the Looney Tunes version. That recognition makes our experience of literature richer, deeper, more meaningful, so that our own modern stories also matter, also share in the power of myth.
I remember a question asked in English class this year: “Why is Greek Mythology still prominent today?” This is a great answer to that question.