I think people lie most of the time to hide something. To hide something that would hurt them in some way either emotionally or physically. Lies are a type of shield that protects us from all of the dangers. For example you are eating on a mall and a stranger comes to your table and starts to ask you questions like how old are you or where do you live you can lie in order to don’t give vital information to the stranger. Another example could be when a friend asks you if you betrayed him by kissing his girlfriend. You can lie to him so that you can still be friend with him and surely to avoid a fight with your friend.
As you saw lies can be very useful as a self defense mechanism. But lies are not only for self defence. It can be very useful to defend other people. For example the teacher asks where is one of your friends. You know that he escaped from classes to see his girlfriend, so you use once again lies. You can tell her he felt nausea and that went to the bathroom, or you could tell her he had to go to his home because his dog he had from his childhood died, or that he had diarrea and had to go to the bathroom.
You can also lie when you don’t want people to know your real intentions. For example when you are talking with your ex girlfriend and she asks you if you still love her you say no even when you know you are dying inside, or when you are in poker and you are bluffing you can say some lies in order to confuse the opponent, or when you are in a business you can lie but in this occasion is not very recomendable to lie because lies of this magnitude can make you go even to jail.
At the end lies could be a very useful wepon or a very bad one. This is because most of the time telling the truth is better. There are really very few times when lying is better. Most of the time is to compliment someone in order to make him or her feel good or to help someone else, but most of the time lies lead only to more lies. In my opinion is better to confront a problem and don’t use lies because then your problem will be so big you will die in the inside.