Sometimes I have to drive after dark in my city, and it never fails that if I drive any appreciable distance that I always see at least one person (often more) driving with their lights off. I do not need to tell y'all why this is dangerous. We're a community of enthusiasts. We know. Plenty of us are driving older cars that predate the tech.
It's not like they don't mandate lots of shit already. Seatbelts, head restraints, airbags, and backup cameras are some of the most sensible things ever required for cars to have. Why are automatic headlights not on this list? There also needs to exist a mandate whereby the lights turn on if the driver turns on the wipers. Because if you need your wipers, you need your lights too. It's common freaking sense.
Your headlights aren't just for seeing, but for being seen. Ambient light sensors are so cheap that they end up in midrange TVs all the time. I blame the backlit gauges and myriad other interior lights. Ergo, it's time to mandate automatic headlights. There's no reason not to.
This is usually the case, but not always. There are some changes that do need to be applied or an exemption requested if the vehicle can't comply. Be sure to follow local laws and don't take anything said online as legal advice.
I was thinking about the high middle brake light on the back of cars. In many places in Europe these used to be outlawed, but people put them on anyways cause they looked cool. When it turned out they were safer as well, they became mandated. At first they were mandated for all cars approved after that point, but some time later it was mandated all cars built after a certain date many years in the past should comply from that point forward. People had about a year to either apply for an exemption or make their car compliant. At that time you would see a lot of cars with a loose brake light on a wire in the back, just to comply.
I also remember a whole thing around right hand side rear view mirrors, which were in legal limbo for a while and people had to retrofit them to older cars at one point.
This is all decades ago, I can't remember recent large scale stuff. Usually the government talks to the constructor, the constructor does a recall and the next time the car is in the shop it gets fixed.
With daytime lights there's usually a module that can be added that always runs power to the lights when the engine is on. On older vehicles with regular bulbs the voltage was like 7 volts instead of the full 12 volts.
However this causes issues with the first couple of generations of LED bulbs. They usually don't come on or flicker due to low voltage.
With the newest cars this is programming option in the car menu as there are a few markets that requires daytime running lights. Sometimes it requires a dealer to make the change with the computer.