I've always wondered what motivates the behaviour to leave behind one's trash. A favourite saying of mine is "All behaviour makes sense". It's too easy to say people are pigs or idiots, but that doesn't get at the underlying values and beliefs that drive their behaviour.
The same people that litter on the riverbank would probably also say that they enjoy fishing and being outside in nature. That is incongruent to me but maybe not to them.
Or why would you go through the effort of carrying in full beverage or food containers, but not carry out the now-lighter, emptier, containers? That is incongruent to me, but maybe not to them.
Is it cultural? Is it family or peer group values that they learned/observed? Is there a sense of entitlement and rights? Is it an act of protest that they can't fish for pinks?
I'd love to have a focus group of "litterbugs" to understand their behaviour. And no, the fact that I was a psychology major in university has nothing to do with it