When you also take into consideration that our brains have evolved from the success that worked thousands of years ago, it makes perfect sense that we are programmed to respond immensely to non-verbal communication.
Adam recognized this, and created this program to maximize our communication skills, with specific focus on body language.
That doesn’t mean he ignores the importance of language, he covers that in great detail, but having the perfect thing to say means nothing if you are ignoring the main method of communicating demonstrating attractiveness and desirability.