Because they want to be like everyone else but have no idea how to be. Also if they are honest as to the kind of person they really are they fear rejection.
In their minds they want to be accepted but be honest is not in their blood. Lying and sounding like they have done a million things sounds better than the world they live in now.
My dad told me at a young age to lie to my mom to get out of trouble. I did not know better….But now looking back I probably should not have listened to him. I told him 16 years ago about this. He denies it. Of course he will because he said I would never tell you anything like that. That is wrong.
My niece is starting the trend. I have told her now nobody will like Franny Fibber. As I call it. She said what is that? Someone who tells stories that are not true. And they will all know about you because you tell stories that are not true. Just be you and they will like you. You are the person they want to know. Not a made up story.