I would not advise people to buy a car or house without making a list. You will probably improve your intuitions by making a list and then sleeping on it.
In a movie, it's often important to have aliens whose gestures and facial expressions can be 'read' by humans. And in the days before sophisticated computer animation, most extraterrestrial bit players were guys in rubber suits. Such practical considerations forced Hollywood's hand when it came to aliens - they look like us for good reasons.