They’re dirt trails or fire roads (also dirt).Horse poo helps the grass grow. Not so much concrete paths tho.
Speaking personally, it is because you're on the way out on a trail you'll be coming back on. Rather than carry a bag of poop for an hour, you just leave it somewhere to pick up on the way back and carry it for 10 minutes.I want to know why people leave their dog’s poop bags along trails. Why bother? Is there a dog shit fairy that’s supposed to come pick them up?
Also, why don’t horses count when you’re asked to “pick up after your pet”? It would take my dog a good 25 shits to equal one massive horse poo (always deposited smack dab in the middle of the trail).