I have never been able to figure out the answer to this question. I wish I knew.
Sometimes the truth hurts<br />
in reply to Rosewater<br />
Not always, I have seen the truth used as a weapon just to hurt. It is the reason for the lie, not always the lie itself that can cause pain. Telling a child that their picture is the most beautiful one you have seen, may be a lie, but it is not hurtful, telling someone that you think they look fat, or that they are stupid, or that you dislike them, might be true, but at the same time, does it really need to be said?<br />
It is the motivation, not the lie, or truth that counts
Many reasons--maybe they feel ashamed of the truth. I knew a compulsive liar and he was trying to cover up his low self esteem.
what is really sad is when they believe it to be the truth.