Comment by ssl-3

Much of that (I'd like to say most) is due to a bad beam pattern and/or improper aiming.

For instance: Round beams suck. The first LED front light I ever bought was nothing more than a flashlight that took 3 AAA cells and attached to a handlebar mount.

It produced a round beam. If I aimed it up/far enough ahead that I could see the road ahead in any meaningful capacity, then it was also blinding to other riders and people in cars.

I could aim it down some and limit others' exposure, but then it was useless at letting me see what I needed to see, myself.

The most recent front light I have came from Walmart, and was sold in Schwinn packaging. It's rechargeable. With this light, other people have zero direct exposure to the LED because it is occluded by the housing.

It uses optics to shape the light. A curved mirror, and AFAICT a lens are inside. The beam it produces is shaped to evenly illuminate my path and it has a very sharp horizontal cutoff.

It's a very sensible design, in that when I aim it at the road so I can best see, other people's eyes are above the cutoff so they aren't blinded by glare. Everyone wins.

But not every bike light has a sensible design. And not every rider has sensible intent.

(The Germans have standards for this stuff enshrined in StVZO, wherein: Stuff like beam shape and cutoff is governed by law. Searching for StVZO lights tends to yield good results.)