Wrong question. Shoulda been, "What's wrong with SOME plinkers?" The people you're griping about are the same ones who shoot holes in signs and mailboxes.
Years ago I ran across a worthwhile comment: "Slums don't make slum people. Slum people make slums." Looking here and there around this country, I gotta agree. So, folks who toss trash are just trash people.
About the only answer across society is, "You can't do that anymore." And we're reduced to mumbling about "a few bad apples" and losses of freedoms.
"That which belongs to everybody belongs to nobody", so there is no sense of responsibility nor attachment to the place of use. Not like at home, where the trash-tossers would be irate if you threw trash into their yard.
Have you noticed that most private ranges are kept cleaner? That private-range fella might not let a trash-tosser back in.