Since I have been doing trailwork, I have cleaned up more TP on more trails than I care to remember. I could certainly fill a garbage with all of it. And as I do this work, I often notice that a lot of the TP ends up (!) in areas that are frequented by dayhikers.
Backpackers are generally instructed to pack all their TP out, and they are required to get a permit that makes this clear. I think that helps. Sure, I still find TP in backpacking campsites--and shame on those idiots who ruin the campsite for the rest of us.
But I find MORE TP where dayhikers stop or turn around. It's clear that many of them feel the call to nature, and respond. Only they haven't packed a ziplock bag along with their 10 essentials.
We've all seen the lists. REI has one. The National Park Service has one. Every hiking association and trail group has one. And most of them are pretty much the same. And in our opinion, they miss a key ingredient.
The American Hiking Organization has its list of ten essential, but it has added one more bonus item: a trash bag.
We couldn't agree more. If nothing else, it will allow you to carry out your own TP. And if you are truly a wonderful person, it will allow you to carry out other folks' trash as well. Because not everyone is a wonderful as you are.
Pack it out, dammit.