By turning away from the need to explain too much, to create, construct and establish, the story opens a space that is not available to the novel. It is the story's signature space of tethered ferocity, the eruption of gesture and repression, the accountant of the unconscious presenting his bill, the Joycean epiphany. It is the reason I call the short story an expansive form, and the novel, contrary to most opinion, contractive. The story says the most that can be said about a restricted moment in time and space. The novel says the least about a great many more.
From Clark Blaise, "The Craft of the Short Story" in Canadian Notes and Queries, issue 72.