When did American movies start trying to clarify absolutely everything? What is our national obsession with trying to provide a psychological explanation for all characters' behavior? If you ask me, I think we have gone overboard. Way overboard. Time to leave that practice behind.
It's refreshing to see a few films recently start to abandon this practice. Miyazaki's PONYO did not try to explain the magic (at least in the version released Stateside). Neil Blomkamp's DISTRICT 9 did not try to explain why the aliens landed here or how people learned their language.
It is fun for the viewer to come up with their own explanations, to discuss these possibilities with their friends. We certainly don't know everything about our world and leaving some gaps in the narrative feels truer as a result.
David Bordwell touched upon the need for spaces in his great essay "Now Leaving From Platform 1" where he explores the hopes of expanding the narrative (and yes, okay, I am referenced therein). Our storytellers really need to take it to heart. It's curious that both of these examples come from abroad.
You can even see Bronkamp employing this strategy in the short film that launched his feature: "ALIVE IN JOBERG".