I've been bothered by too-bright headlights for some time now. As has been pointed out, the reasoning for this is the brighter headlights in-use. This is actually not the case. While some headlights are like that, the main problem is actually standards in diffusion.
When headlights are used, the light is diffused in a specific pattern. IIRC, vehicle headlights usually tilt to the right to give greater brightness during turns or something. Each car-manufacturer had their own way of doing the diuffusion, and someone decided a standard would be a "Good Thing"(tm).
The European's went first, and started standardizng diffusion patterns throughtout Europe. Complaints at their repective agencies went up for approximately three years. When they stopped, the assumption was that people got used to it after a small period of time, and the standard pushed forward. The US car-manufacturers guild (or whatever it's called) has agreed to this new "standard" and all US car's have a newer diffusion pattern. The assumption is, that it only takes three years for people to get used to it.
Height has not been standardized (enough) yet. But there is a lower and higher limit.
My source is the outer-lamp section of a car-manufacturer. But he gave me a link, which i do not have on me right now.
My wonder is, if people stopped complaining because they got used to it, or they realized it wasn't helping. And, even if people did get used to it, how can anyone sit so high and decide what is better.
UPDATE: This can be seen at the Department of Transportation's Docket Management System, where a Simple Search can be done for Docket 13957. The top line is the doument, and there are comments on it as well.