Cabel writes about a phenomena that you've probably noticed at one time or another. See, if trash doesn't hit the ground, it's not littering …at least in some people's minds. So the discarded paper cup or wrapper or bottle gets stuck in some space above ground or in receptacles that aren't trash cans.
Now, I can understand how generalized holes — containers, street light bases, flower pots — become makeshift trashcans. Even if they’re obviously in no way trashcans, and likely will never be emptied or cleaned by any human being on earth, and in most cases there’s a real trashcan mere feet away, they at least share a vague similarity to the raw concept of a trashcan.