Have you ever seen someone or you yourself followed someone and had the person in front turn on their lights? In daylight and panic situations, it is hard to distinguish between someone turning on their lights and someone depressing their brake pedal on a car without a third brake light. I've seen people hit their brakes when the car in front turns on their lights ... it's funny to watch, but it happens. I've turned on my lights before to get a tailgater off my a$$.
Having a third brake light makes it idiot-proof as to when someone is actually hitting their brakes versus someone who is merely turning on their lights.
