Culture can be extremely hard to change.
“The public signs in America threaten, beg, and fine people to just put their garbage in a can. Surveys also point to the top 3 reasons why Americans litter. 1) Laziness. 2.) There is already garbage on the ground. 3.) Somebody will pick it up. These are reasons that never even occur to the Japanese. In Japan, they want you to “not litter”, but they also want you to keep your garbage and take it home with you.
To reinforce this behavior, the common signs in Japan ask people to take their garbage with them. Then, to reinforce the sign, they usually have no garbage cans in the parks. So when faced with the choice of throwing their garbage on the ground or keeping it with them, they keep it. They don’t need a “Don’t Litter, Keep Japan Beautiful” sign. They have been doing it their whole lives and are used to taking their garbage with them.”