Here's what happens. Someone takes their dog out for a walk. They're good middle class people so they bring their doggies poo bags with them like they've been told to do. Ooh, simon is going for a poo.
Adopt a grimmaced expression, put bag over your hand, grab the poo (don't look at it though), fold the bag over and tie it up. Now look around for a bin. There aren't any! Well that's just ridiculous, don't they know these woods are popular with dog walkers!!?? Well i'll just hang it on this tree and take it back to the bin in the car park on the way back.
"Come on Simon, walkies!"
Carry on with the 400m walk thinking about all the things the the modern day person has to worry about..have we run out of garlic cloves? Is there any peso left? Tsk! I can see that girl's tummy, etc, etc.
On the way back, with all this running through the walkers head they've forgotten about the bag of dog poo and allow themselves a little shake of the head at the state of the world when they see it hanging from a tree and the selfish people who put it there.
"Come on Simon, veggie chum for tea!"