Despite all the debates as to why the Gospels were written (ranging from conflicts in a so-called Matthean community, synagogue expulsions, identity formation, to counter the rise of Gnosticism, etc.), I still think one of the best reasons calling for the Gospels to be written was to tell the story of Jesus for a generation who did not know any of the eyewitnesses or have access to first-hand accounts of the Jesus tradition.
Have you read Robyn Faith Walsh's new book? Great piece of scholarship - but way to skeptical for me.