Littering, no doubt.
I seriously doubt your parents taught you that about smoking, unless of course your parents are only about 30 years old. That would make them part of the generation that has been brainwashed by all the anti-smoker hogwash no one can get away from any longer.
The overall trend is there and has been for many decades.
As a group smokers are less educated and poorer. Smoking is about as “down scale” as you can get.
As a group smokers tend to be litterbugs.
Stinky littering undereducated and poorer is a sorry way to go through life smokers.