Of course if you get your movies from iTunes then Apple put on their DRM (bless them). They have no desire for you playing the movie you have just paid good money for on anything other than their hardware!
Oh quit the stupid, idiotic Apple bashing will you !
Its not Apple's decision. Having DRM in place is a requirement set by the content providers in the contracts that Apple signed with them.
Plus its not strictly true anyway.... there are cables available !