This builds familiarity plus the conversation will invariably entail an idea or feeling that can be shared with the audience. Another reason is that many people have not learned to be themselves before an audience. They need to become as familiar with their persona as with their face in the mirror. Most laugher is not a response to comedy but rather an attempt to set a positive emotional tone and enhance feelings of group belonging. People are born hardwired to laugh.
Babies start at about four months, when peekaboo gets a response.
By contrast, a sense of humor is learned. It is a skill and must be practiced. See United States Laughter Clubs for a list. Have a good laugh at the beginning of each day by visiting one of the many humor sites, such as the Comedy Zone. Surprise your family, friends and co-workers with puns, parodies, props or pranks.