Rear Fog Lamps

We live in a vast area that receives a lot of fog. Why do our North American vehicles NOT come with rear fog lamps? It is a safety feature that they have in Europe and SHOULD be used here.
Richard F 12/21/2012
I have a relative who had a car with rear fog light. It's just one really bright tail lamp.. and in fog it's easy to see even when you don't see the other tail lights. I would like to see this on U.S. vehicles as well