People were pushing for those in the 90s. I think it never got adopted because of the loss of transparency on the windshield (AFAIK, there's an international standard that most countries go beyond, and it's way above 50%).

There is also some dispute over the direction, because polarized sunglasses filter out horizontal light, but we would want this system to filter out vertical light because of the way things reflect. I guess this wouldn't be a showstopper to turning it into law, but it was loud at the time.