I would add scooping dog shit is another test. There are people out there who will bag the shit and then leave the bag on the ground for the poop to steam in for a few days before they put another bag right next to it to keep it company.
Not defending this, but some people intend to pick up the bag on their return, presumably as they are headed away from a trashcan and will return to one on the way back. They don't want to carry it the whole time.
They should just carry it the whole time, or return to the start then and there to drop it
some people intend to pick up the bag on their return
If that's the case and they don't forget, then I am firmly on their side. Literally no one is impacted if the bagged poo sits there another 30-60 minutes...
Sometimes people walking dogs plan on walking past the same spot on the return trip, so they leave the bag. Sometimes they forget to pick it back up, or forget that they dropped it there and take a different route home. Sometimes bag number two is the next day, or some other person's bag. Generally, if someone's going to pull a shit and split, they're not bagging.
Environmentally, the bag actually prevents biodegradation. If you don't pick up your dog poo in the wilderness and not where people step, some shit-eating insect (like roley-poley or cockroach or a worm) will eat it all up within a week.
Which is worse, the ones that leave a bag (perhaps unintentionally) or the ones that just don't bother with the responsibility at all? When I had a dog I not only would clean up behind him, I would leave the bag untied until the end to capture what I could of the inevitable left piles I would run across. I'm sure cart return, dog poop, fast food containers, and the old cigarette butts are all under some human psychology grouping of ego superiority.
I think leaving the bag is worse. When it is just poop, maybe the dog ran out of sight or was loose or the walker ran out of bags or whatever. When it is bagged, a human made a decision to scoop it and then leave it on purpose.