I'm sure you were told as a child to look the person with whom you were talking in the eyes. You may have also been instructed to deliver a firm, yet gentle handshake, not a limp one. I bet you were told to smile, too. Your guardians wanted you to come across as likable, because being likable would get you far in this world.
All of these lessons you were taught as a child apply today. Now that you're an adult, …
Source: Recruiter