So? An actor's behaviors would be convey no information if we did not already recognize them as real-world indicators of status. While the high-status/low-status continuum outlined in this post is constraining and is in no way a definitive representation of how people project status, it is a useful metric and broadly true. If we imitate actors, we are imitating a simulation of an appearance of how high-status people act, not a fiction.
To put it simply, high-status people do these things in real life and that's why these behaviors are reflected in the movies.
A couple other thoughts:
Even if our indicators of status are socially learned, it doesn't diminish their effect whatsoever.
(Warning: abstract speculation) To an extent social interaction is at its core a group of minds playing roles as various actors, exchanging emotional, physical, and intellectual information through the medium of this play called 'social interaction'. This process is most fluid when it is all subconscious and there is no separation between the mind and its acting role, but we should not disparage actors as displaying 'simulated' behaviors when we ourselves are nothing but actors using the same sort of tools to express ourselves.
Of course Johnstone isn't making these things up out of thin air. But he developed that work for the stage, and what happens on stage is not reality, it is a simulation of reality. And a simulation intended, not to be faithfully realistic, but to tickle the audience, and I think that the idea that an audience wants to see an actually accurate picture of reality on the stage is one that does not exactly jibe with the general views held on LessWrong. (Try it on Overcoming Bias, and I'm sure the instant pattern-matching response will be "fiction is no...
I can't remember how I found this, just that I was amazed at how rational and near-mode it is on a topic where most of the information one usually encounters is hopelessly far.
LessWrong wiki link on the same topic: http://wiki.lesswrong.com/wiki/Status
Source: http://greenlightwiki.com/improv/Status
Retrieved 20 March 2012