I've never seen a traffic light burnt out.......what gives?

Traffic lights do burn out. That is why you usually see 2 signal lights in major intersections- In case one burns out. However, newer traffic lights are using modern LED bulbs. Each “bulb” is really about 60 little l.e.d. bulbs. All closely aligned, but independently powered. That way, when a bulb does go out [and it does happen], it’s just one dot out of 60, and the light still works just fine.