Because IMDb don't offer anything of their own.
NEW: alternative. You can call search?q=foo to find all movies with 'foo' in their title; eg search for 'matrix'.
Pass an IMDb 'tt' ID to get anything useful; eg:
NB: all support JSONP/callback; just add a 'callback' argument with the name of your callback function; eg /search?q=matrix&callback=foo.
Written by Peter M Howard (http://wintermute.com.au/).
Uses Davide Alberani's IMDbPY.