Ok so I know I'm late to this thread, and It's been really fun watching everyone debate headlights and what they "feel" is how they work, but in reality it's much simpler.
Watch this video, they explain all the different types of bulbs and how they work, as well as the different housing designs.
I'll summarize a couple points below.
1.) How the headlight is aimed plays a major role, and is something that can be adjusted. You might see a car with one headlight blinding you, when the other isn't, this is likely due to a housing being replaced from an accident.
2.) Housing designs reflect the light from a bulb in different ways. Reflector housings (normal style) have the light reflect into a mirror and then shine out (usually just one reflection). Where the bulb emits light is crucial for this design to work. Sticking HID and LED bulbs into these housings without accounting for their different shape and emitting area will cause the light to lose focus, and glare. It will also drop the output in some cases. Projector housings gather the light in a parabolic mirror and shine it straight out, limiting it's output using a shied inside. These housings are less prone to glare as the cut shield always stops the light from above a certain point, but the bulb still needs to emit light from the right area for the unit to be effective.
3.) Not all bulbs are created equal. Halogen bulbs emit light ONLY from the filament, and they emit in a 360 degree pattern from that spot. HID bulbs use an arc to emit light, which is usually longer and wider than the area of a halogen bulb. This is why they glare so much in reflector housings - the extra output can't be controlled or focused properly. LED bulbs suffer from the same issues with cheap designs. They need the have LED chips that match the location and size of a halogen filament, while also being thin enough to appear as 1 light source with as close to 360 degree output. The newer, more costly bulbs are good at mimicking the halogen emission area, and can give good results when installed into regular housings, but the culprits you're seeing probably aren't dropping $200 on their bulbs.
So, new fangled lights aren't trying to kill you, and if someone crests a hill and you get an eye full relax, it happens to everyone. If you see a d bag with ebay HID bulbs phone in their plate, enough of those will run him a VI and a nice ticket.
SheepStar