I'm sure lying is a popular defense technique, but I think really smooth liars somehow have learned to sort of disassociate themselves from (or never learned not to in the first place) emotionally understanding the impact of their lies.
There are a lot of different reasons people lie.
I lie...
...to save my own ass
...to get out of having to do something I don't want to do
...to blend in (pretend to care when I don't)
...to protect my privacy
...to shut someone up by telling them what they want to hear
...to manipulate people
...for personal amusement
...to get a reaction