Jazz Hands In Traffic

Why do people who are talking to someone on the phone use their hands? Ya know, hand gestures as if they were in front of the person? I was sitting at a red light the other day and this guy behind me looks like he's trying to fight off a swarm of bees while talking on his cell phone. This is the kind of behavior that frightens people. The person you're talking to can't see you, okay?

I'm talkin' on the phone!