UIs In Movies And TV Shows

Why do movies and TV shows use custom graphical user interfaces instead of Windows or Mac OS X? To make it look cool? To avoid paying a fee to Microsoft or Apple? You would think it would be easier to convey what’s happening if they used something with which people are likely to be familiar. Tip to the people designing these things: Computers don’t make sounds when they do stuff. There isn’t a little beep every time the cursor moves, and text isn’t typed out like a typewriter. I know you know this, because you used Windows or Mac OS X to make those effects.