Games are interactive, and demand more attention & mental capacity then more passive non interactive media. Perhaps we need to be reasonably unsubtle with the communication in games, as players engaged in the game will miss the subtleties.
This advice for acting in RPGs might seem too obvious, for most players these clues are clear;
“Gesture. If acting as a lawyer, point with your pen. A politician might point with her glasses; a police officer might tap his notebook; an annoyed or frustrated man will rub his eyes.
Nervous people play with their hands. Liars look away. Angry people lean forward across the desk at the DMV, throw their registration papers down, and yell, “I paid my taxes!””
Danny East, via http://www.roleplayingtips.com/