<a href="http://www.smbc-comics.com/index.php?db=comics&id=3038">SMBC</a> puts some very interesting words in the wizard's mouth that explains his role quite well. After Dorothy and Co. have revealed him to be a fraud---a mere man rather than the all-powerful wizard they'd imagined him to be---he says, <bq>[...] Now then, you can either persist in your dull revelation, <b>or</b> you can close the curtain and return to your world where good and power can allow without wicked dross, and where the broken vessels of your lives can be made whole by the caprice of an inscrutable demigod.</bq> I think it's safe to say that not many of us persist in the dull revelation.