Someone from Germany please correct me, but aren't you required to keep the street in front of your house clean? I was amazed at how clean Germany was, then I went to Switzerland, even cleaner. Amazing.
However
There's one class of people who believe that it's their God given right to litter wherever and whenever they want, and that's smokers.
You can especially see it around Tram stops where people are waiting around and will quite happily throw their cigarette butts on the ground or pavement when the tram approaches.
Usually between 5 and 6am, that helps keep them clean, too.
(I’m a German who usually wakes up from the sound in the morning)