The lighting is almost exclusively enhanced with HDR on only. This is particularly the case with aircraft taxi lights, landing lights, airport ramp lights, and road lights, as well as car lights and their light cone cast. I would venture to say that as aircraft makers have started to update aircraft to the X-Plane 10 specifications, you are only just now coming to realize that HDR is required for the nice effects we desire. Doesn't hurt to turn it on and see what happens in a night scenario for you...