The house is not a garbage can

Why is it that my kids cannot put their wrappers, papers, and other junk straight into the garbage can? The worst times of the year are Easter, Christmas, and Halloween, when they get candy and they drop their wrappers on the floor wherever they choose to eat (which SHOULD be only in the kitchen, but somehow that never happens either). They also throw their wrappers behind the sofa and piano--is that any easier than throwing them straight into the garbage can?

I was very happy to see Mr Z (the youngest) pick up a candy wrapper off the street all on his own when we were downtown so he could throw it away. He's the only one of my kids who seems to have a gut feeling that tells him that you shouldn't mindlessly drop garbage on the ground.