[TeMPOraL]

Even in the most well-behaved country, everyone will drop some litter at some point - even if through hurry or accident. When you multiply "once every thousand opportunities" by city's population density, you still get a lot of litter. Add to that people who're drunk and people who simply don't give a fuck, add random spillage (e.g. wind knocking trashcans over or pulling trash out of them), and you get a visible fraction of litter simply, probabilistically caused by just so much trash being produced.