Because lying is their hobby and they can't stop it.

EmilioLargo, this an interesting angle and funny lie being hobby make the person most dangerous fellow to work with in life.
Have you met this kind of person? 

I also agree with you ..... very useful information for us ...... keep it up thanks for this..........smile

People tells lie because they do not face the others.

To run from the harshness of Reality?!

Lying is another human trait and people do it for many reasons. Lying is being used by many people so often that it has become second nature to them. Sometimes, it just comes out naturally and they can easily deceive those they lie to. unemployment

People lie because they do not dare to face the truth. Truth is
hard than  the lie but it delivers internal peace and satisfaction.

i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later
i will tell you later vv

It depends from the situation they were in.

Kids actually lie to not be punished by parents.
Teenager lies to be accepted by friends.

Because they have everything to lie and possibly simplify their lives.

Lying is morally wrong and is always discouraged. But, unfortunately it is quite commonplace and comes naturally to human beings. It is ironic that deception is considered 'fair in love and war'. But, lying or deception always has serious consequences. People lie because of personal and social reasons.

People lie for a lot of reasons, most of which are not intentionally hurtful," Serota says. "People lie to avoid others, to protect others' feelings, to protect themselves, to promote themselves, or for some personal gain (and sometimes for the benefit of others)

However, of the most common motives for telling lies, avoiding punishment is the primary motivator for both children and adults. Other typical reasons include protecting ourselves or others from harm, maintaining privacy, and avoiding embarrassment, to name a few.

Sometimes it's to protect the liar from being punished, or to protect someone else from punishment. The lie might be to avoid being embarrassed, to hide an awkward situation, or to simply have others think better of the person telling the fib. ... Researchers say there are various reasons why some people lie compulsively.21-Oct-2019

However, of the most common motives for telling lies, avoiding punishment is the primary motivator for both children and adults. Other typical reasons include protecting ourselves or others from harm, maintaining privacy, and avoiding embarrassment, to name a few.