They ARE fully parts of reality, but only by virtue of their effects on human thought, language and behavior. All myths and stories function of analogies of certain thought-formulas or series thereof. They illustrate specific narratives that can be safely regarded as contingent parts of reality that correspond to the social-material relations that they promote. Furthermore, a human only develops the capacity for full reason after having explored a myriad of fantasies as a child. Reality is approached first through fantasy. Only after that can fantasies be set aside by reason, unless of course one is severely escapistic or psychotic. As adults we learn to distinguish which of our fictions correspond to which things in reality as they exist in conjunction. That's how we come up with more engaging narratives.