Most states have a law that requires headlights to be turned on whenever you use your windshield wipers.
I'm not questioning the law itself. When it's raining, visibility is low, so it's critical that every car have it's headlights on. That's not the point here. What I find interesting is that most cars still don't do this automatically.
If a driver turns on his windshield wipers, but forgets to turn on his headlights, he not only risks the burden of getting a ticket, but he may cause an accident.
While there may be some cars that do this automatically, the majority of cars produced today still don't do this, and they should.