I think reflectors and reflective materials are so very important. An ANSI-rated vest or jersey helps give the oncoming driver more perspective that there is a person up ahead. Quite often I see what appears to be a disembodied light looming somewhere out in front on me on the road. Of course, it's the light from the bicycle but that's all I see.
In my opinion, reflectors give an added dimension to the bicycle and the cyclist. If I were approaching that same cyclist who was also wearing a reflective vest/jersey, rear reflectors, reflective tape on helmet, etc., I could see more form and definition from afar.
Car headlights are very powerful and the right reflective materials are like adding multiple lights to your bike. That's why I scratch my head when bicycle shops take off reflectors on new bikes because they are somehow considered a nuisance. I can see very well on city streets in the dark and use blinkies for the front and back. But it's my vest, I think, that make motorists take heed. I've noticed the difference when they go around me.