I live on the 4th floor, and at night I can directly see the light sources of all the road lights outside my window. There’s just no way this is necessary. And then there’s the glowing sky over Hamburg’s busy port. And all the shop windows at night. And so on.
This excellent piece in The New Yorker from 2007 points out all the serious effects of light pollution: It is disturbing sleep, causes health issues, benefits crime, costs a ton of money, wastes energy and endangers animal populations.
Most people don’t notice bad nighttime lighting; if you do, it can make you slightly crazed. When I’m driving at night, my wife has to tell me to watch the road instead of looking back over my shoulder at a yard whose trees have floodlights in their branches, or at an empty parking lot so bright that you could deliver babies in it