fog lights
Nate said it all.
Fog lights are a safety feature designed for increased visibility in the fog. They are aimed to light below the fog, to minimize reflection and increase visibility of the roadway and markers. This is also the reason for the traditional yellow foglight tint - less reflection of the water in the air, than with white beams.
Since some people apparently don't know, bright lights are unsafe to use in the fog, heavy rain, or snow (when fogs are helpful).
So it's common sense that fog lights should not be switched with brights. It may cause an accident and destroy your precious 3! Not to mention, you or someone else. This is why it's not a stupid law.
Besides, it's rude (not to mention needless and potentially unsafe) to use fog lights in normal driving conditions when traffic is oncoming. Just like giving attitude to a stranger, or blowing smoke in someone's face. You like getting smacked with blinding lights in your eyes when you turn a corner? Yeah, temporary white-out and loss of control - good times, eh?
If anyone flashes their brights at you when your fogs are on in clear weather, this is probably why. But - you probably think they're a**holes, right? Hmmm... Okay....
If you can't see enough immediately in front of you with brights on, then get rid of the full 20% tint on your windshield.
Or take off your sunglasses at night.
Or hotbox when your car is NOT moving...
etc.