Why do they lie?

When I watch some movies, I think about stupid men's behavior.
Sometimes... No no. Almost times they lie to person who they love, Even If they didn't do anything wrong. Why do they like that? is it looking good? Finally, their lie is found by other person. No men make public their lie by themselves. Yeah I think that is very very fairly good. B/c that is movie.

Honestly, I think telling truth is the best way to send their emotion. Not a lie. Is it necessary to hide their honesty? If they do like that, it will make a lot of misunderstandings, and it could destroy their relationship. In my case, always I try to be honest. Sometimes it doesn't work well, but every time I try. Honesty is better solution to communicate feeling with any person.