Physiognomy is the study of the traits of the face. It is a great insight into personality styles and communications techniques. The more you know about your clients, family and audiences, the easier it is to engage with them on their comfort level.
Imagine being about to meet someone for the first time and know how fast or slow to talk; how much or how little information to deliver; how close or how far to maintain distance between you; whether your information should be analytical or descriptive and hundreds of other insights a face reveals.