Nothing but the Truth

Why is it that some people can not tell the truth? Even if they know that they are going to get caught in the lie, they will still tell one.
I can see smaller children not telling the truth because they don't know any better, but for adults - there just is no excuse.
I know one man that I can tell you what he is going to say before he ever says it because he doesn't know honesty if it jumped up and bit him on the lips. He was entrusted with some papers that were of importance to someone other than himself. My husband told me about this and I said, "I bet he throws them away because they are not having to do with him. Then he will make up some lie if the papers are ever needed again." Well, less than a year later my prediction has come true. He swears that someone stole the papers. Why would someone want to steal papers that had nothing to do with them? But then again, why would anyone ever trust this man with even toilet paper?
I pride myself with being honest. I don't break laws, I drive the speed limit, and I have the utmost respect for other people's property. I don't think it is asking too much to expect this same courtesy.