Part of the problem stems from the fact that as cars age the headlight lenses oxidize and the original bulb's light becomes insufficient to light up the road ahead of the car. Some drivers are fixing the problem by swapping in much brighter aftermarket bulbs as opposed to replacing or resurfacing the lenses. It's easy to verify this by looking at the headlights of the offending cars after they've parked.
There are a few products that clear that up. I remember my mechanic doing it for me and it does make a noticeable difference. I would think any auto parts store would offer it to anyone buying bulbs as an up-sell.
