Here, in other words, is a long-range backstory—a device that, in the Hollywood of recent times, has grown from an option to a fetish. I lost patience with “Charlie and the Chocolate Factory” once we learned of Willy Wonka’s primal trauma (his father was a dentist, and forbade him candies, so guess how he reversed that deprivation?), and, likewise, with “Batman Begins,” from the moment that mini-Bruce tumbled into a well full of bats. What’s wrong with “Batman Is” ? In all narratives, there is a beauty to the merely given, as the narrator does us the honor of trusting that we will take it for granted. Conversely, there is something offensive in the implication that we might resent that pact, and, like plaintive children, demand to have everything explained. Shakespeare could have kicked off with a flashback in which the infant Hamlet is seen wailing with indecision as to which of Gertrude’s breasts he should latch onto, but would it really have helped us to grasp the dithering prince?