I always try to pick up empties. They're difficult to find sometimes. If you're standing in water, they take on water and sink too. Leaving a pile is littering. Leaving a couple you couldn't find is typical.
In a free society, it is not the obligation of the citizen to prove to the government that he is a good person. It is the obligation of the government to prove to the rest of the citizenry that the citizen is a bad person, with probable cause.