Why do movie directors talk to their actors while filming?

I always see in behind the scenes of movie the director talks and directs the actor, (example) "You see him and your scared, start to run, BOOM! You've been hit" and the actor goes with it but I always wonder why the directors voice never turns up on the audio. Thanks.



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Because they can...plus, most of time they are probably giving stage directions to the actors on how a particular scene is to be shot. Or if the actors should have more or less reaction to get the best shot possible. It's actually pretty cool seeing the interaction and joking. Especially on the blu-ray edition of the A-Team.