The beer cans or pop cans I don't mind picking up, they are worth money for the deposit or so much a pound.
Food waste causes problems with bears and other pests.
While up in the Olympic Mountains in the State of WA, our group came across a campfire that had jumped the fire ring rocks and was smoldering through the fir needles heading for the timer. Took us a few hours to put it out before we could set up camp.
The worst offense that I have come across to date was in the Cascades in OR. Some campers had used a small creek that was about one foot wide as their outhouse. There was human waste and toilet paper in the creek and on the side banks. Sorry, no I did not clean this one up and did no prospecting in that creeks water!
A little respect for our " GREAT OUTDOORS " gos a long ways, after all we own it. Ron