I'm probably preaching to the choir here, but what the heck...
Over the years my wife and I have gone to the high Sierras to camp, fish, hike and just "get away". While going to the middle of nowhere wasn't our objective, we did go to camps that had sites you could reserve, lakes or rivers, etc. You know, "God's Country"?
Yet for some reason we eventually ended up carrying some plastic garbage bags along in our day packs. That would be to pick up some of the trash we found along the trail that marred the beauty of the place. We got into the habit of just picking up some stuff left on the beach or on the trails each day which we carefully dumped into the garbage cans to thoughtfully provided by the camp hosts and so miserably ignored by some of the campers who visited before us.
It still makes me mad but we still stuff a garbage bag into our day packs and still try to pick up trash left behind. We did the same thing when scuba diving; after the dive was through we'd dump out the contents of our BCs on the deck of the dive boat and unload the stuff into the trash. It really impressed the dive captains and crew and I think kinda embarrassed the othr divers...but picking up trash is somewhat interesting...while grabbing a beer can in a hole in the reef off Tortola, I happened to find a very nice new dive knife and sheath. The captain said no one had lost it off his boat so I was entitled to keep it.
One mans trash may lead to another mans treasure....so if you see stuff by the side of the trail, pick it up if you can....for karma if for no other reason!