I've never understood this gag. Are there really people who are so intimidated by cars that their iq drops twenty points when they get behind the wheel? I grew using a riding lawnmower so driving a car was a bit nerve wracking at first, but that was it for transition issues.
YES. You ever heard of the TV show "<nation XYZ>'s worst driver"? There was a person on one edition, had a license and everything, been driving for years. When in a test situation where they had to avoid an obstacle, they ended up just stomping on the throttle, taking their hands off the wheel, and covering their eyes. They ran over the host of the show, and almost ran over many other crew members.
Thankfully no one died, but these people with non-functional brains when behind the wheel exist, even among people who have a license.
Edit: You know, I don't even think this is the one I was thinking of, it might have happened a few times...