It’s actually very important for headlights to not be diffuse. As their job is the very specifically throw light dozens of meters away in a very selective cone. The idea is to light up only the road and nothing else. Headlights usually achieve this by having multiple sets of lights inside. There are the main beams that light up the road in the distance. Wider broad beams (usually achieved with a lens) are used that light up more area near the car. This helps a lot with lighting up road sings and such. There’s also side beams that light up the sides of the roads. Depending on the exact sort of headlights, there can be even more. Like smart lasers that selectively highlight some stuff.

If one were to just blast diffuse light in all directions, it would not light up nearly as much of the road ahead. Which means they would need to be way more bright in order to do their job. At the same time they would blast out light in useless directions, wasting energy. And would make people getting blinded by lights even worse as all that light that would otherwise be pointed down, point straight into people’s eyes. But not just in the oncoming directions, but in all directions.

A diffuse light is good for being seen, but not good for lighting up a specific area. A directed not diffuse light is hard to see, except from the one direction, but is very good at lighting stuff up.

The issue with most car lights has nothing to do with the lights or the cars. It’s the idiots driving them. So many headlights are set way too high or not aligned at all. People often intentionally set them higher, because it helps them see, but hurts everyone around them. Another issue is the amount of light being put out is way too much. In the past, the amount of light would be pretty low, so people’s eyes would adjust and letting them see everything. However with more street lights being placed to help safety and these street lights also using leds and becoming brighter, it was harder for people to adjust to the light and thus needed more light for themselves. It’s like an arms race where we keep adding more and more light, which is terrible for everyone (including nature). In the end it’s lack of regulation that hurts the most. Brighter wider lights sell better, because people driving like them for the better vision it offers. Even people that get annoyed at being blinded by others. If people like them, it drives up sales, so cars get designed with brighter headlights. Same for cars getting bigger and bigger. And those bigger cars have the headlights higher, increasing the issue as well. Market drives into lunacy.

I fucking hate cars, get blinded by headlights all the time and think something should be done. But diffusing the lights is definitely not the solution.