**** shame isn't it. I've spent most of my life hauling out other people's trash and litter. I usually carry a trash bag with me and pick up the thrash on my way back out.
Here on the Cape Lookout National Seashore, the state's open container law is the cause for a lot of the litter. As a boater, you can be caught with a boat load of beer on board as long as none of them are open. But if there is even one beer open you can be cited, So, the folks go ashore, drink, then leave the cans or bottles or just "sink" them. Usually they bury them but they soon are uncovered by the tides.