Alright so, since I've noticed a lot of littering left here and there, I reckon it's because many are uninformed of how the actual area clean up works.
1) Area Clean Up only deletes loot bags, that is the containers dropped upon dead monster. Not individual items dropped. If you drop a torch on ground, it will stay there indefinitely, so rather leave it to the loot bag because that will be deleted after you leave the area.
2) Chests delete previous contents after it has been triggered by another player in 10-15 minutes since it was closed. So any trash found in them can be left in them, again any items taken out and dropped to ground will not be removed.
So they are the trashcans of the planes, feel free to utilize them even if they do not delete contents immediatelly, they will clean up after you.
Littering: How Area Clean Up Works
