I fished almost every fair weather weekend for 20 years before getting tired of it. Stripped fishing line, worm boxes/cups, lure packages, you name it and someone left it behind at 90% of the spots I used to go to. I agree it's not the sporting event that is the issue it's the person. I'm in the city on a main street with a bus stop, garbage, paper box and intersection. Every day SOME people just drop their garbage on the sidewalk, shelter, or my driveway, even though the garbage can is right there!
On the other hand I've seen a woman lately who walks down the sidewalk on garbage day and puts street garbage into peoples cans as she goes down the street piking things up. (I only spotted her twice as she was in our can and people have been known to leave extra garbage in ours due to the bus stop and our garbage get's tagged rather than taken. Ya, it's that bad when people drive around and leave garbage at a bus shelter or in anthers bin because THEY don't want to pay for it.) I didn't say anything as we used to do the same thing on our walks, but it wasn't the purpose of the walk like it seems to be for her.
Some people pick up after themselves without being told. Some only do it if they know they are being watched. Money, life style, or ownership doesn't seem to matter but how they where raised does at least for a few when the conversation comes up. Same goes to giving a hand to a stranger, offering a seat to an elderly person or a woman that's with child. I've seen high-end lawyers who don't wash their hands even after leaving a stall and Tim's staff who wash before they serve another customer. Upbringing or culture is the only thing I can think of that makes a difference in the large scale of things. The rest are just a$$hats who think it's all about them.
Maybe I should start walking more again...