Why people lie ?

Why do people lie ? We know thousands of reasons and yet is there ever a time when a lie is right ? or are they always wrong ? and why is what we call a small lie considered a 'white lie' what does that mean. Is there a difference because of the motivation - e.g. self preservation, fear of harm as opposed to the will do whatever it takes person to get what they want sort of lie? or the 'I'll teach you' nasty type of lie ? Have you ever googled 'why people lie' ? its like the hottest topic evvvver...there is like info on 'lies to save face' 'lies to shift blame'....what about when professionals lie to achieve the end result, does that not disregard the whole process of what is fair and equitable, just? isn't that basically lying to get one's way.....I have done it and I don't know a person who hasn't as a child.... then we grow up...well some of us....why do women/people feel the need to lie about their weight, the prices of purchases, the real ! colour of their hair oh....and their age? is all of this because some people are so scared of the truth?