Why lie?

So, in general I think it's strange to lie and I'm a horribly obvious liar. I just can't do it I can't keep a straight face. But there are so many people who lie about stuff that doesn't matter. Like when checking someone's I.d. I frequently notice when they are clearly shorter then me (5'5") and yet their I.d. says they are 5'9". What's the point of that? It doesn't matter what your I.D. says you're still short. If anything that can be harmful because I can deny your I.D. if there is too big of a difference. Like I am shorter then my drivers license says but only by a half of an inch and only because I had a tumor that bent my spine and made me shorter. So I don't get those type of lies but I also don't understand the bigger lies. Like, why? 99.9% of the time your lie gets found out and then your worse off then you would have been had you been honest in the first place. I also don't understand talking behind someone's back. Guess what if I have a problem or issue with you that is a big enough deal that I'm talking about it, then I will talk to you about it. It's far more satisfying to work out your differences as opposed to talking behind someone's back and just getting more bitter and not resolving anything. So don't lie. There's almost never a point to it.