Why do people lie to each other?

"According to Dr. Gail Saltz, everybody lies. It may only be “white” lies, but everyone tells lies or “omits the truth” sometimes. We start lying at around age 4 to 5 when children gain an awareness of the use and power of language. This first lying is not malicious, but rather to find out, or test, what can manipulated in a child’s environment. Eventually children begin to use lying to get out of trouble or get something they want. White lies, those concocted to protect someone’s feelings, are not a big deal at all. The person, however, who seems to feel compelled to lie about both the small and large stuff has a problem. We often call these folks pathological liars (which is a description, not a diagnosis). They lie to protect themselves, look good, gain financially or socially and avoid punishment. Quite often the person who has been deceived knows that this type of liar has to a certain extent deluded him or herself and is therefore to be somewhat pitied"