Hazy Headlights

They say "This easy-to-use, rich gel formula quickly restores optical clarity to both rigid and flexible clear plastics." Great, but if the headlight lenses didn't mist up over time, we wouldn't need products like this. So is this the "price" we pay for cost-efficient manufacturing processes? Anything that reduces the extent of injury in an accident is good thing, but replacement headlights are expensive! Can any product keep plastic lenses clear forever? What's the solution?