So as the title says..

Somehow since I've started to notice one, it multiplied by a dozen. Why do people do this to their headlights? Is it really for the design as like they want all black in the morning then a dimmer light in the evening or is it that their headlights are really bright and they use a tint to make it a bit dimmer. I'd like to know what are your reactions or say about this. Cause for me, I find it a bit ok for the aesthetic purposes but it denies the headlight of its proper use.