As a teen I worked in McDonald’s mostly looking after the eating area. The expectation is that people throw away their own rubbish and we’d wipe the tables. Throwing the rubbish is a pretty easy thing to do but so many didn’t.
I wonder if it’s something to do with peoples’ perception of respect – some think it’s beneath them? Seems to me there’s a pretty strong correlation between how well off you are and how likely you are to deal with your litter – for some reason the worse off are more likely to think it’s beneath them, the better off not.
I used to live near Hammersmith and the litter on the main shopping street there at the end of the day was often unbelievable – a lot of council estates around there.