They don't need to be in a hurry. Their food isn't going to run away - leaves and fruit. Having a slow metabolism, they are thus able to exist on very little food. They don't have many natural enemies. The algae in their fur makes them very hard to detect in the tree and, being able to make a surprisingly fast swipe with their vicious claws, they make formidable prey for a harpy eagle or snake.
Well Boo now that would be telling!! but if I was up a tree and it was going to take an hour to get down and then another hour to get back up just for a poo, Im sure I could poo from up the tree without hitting the branches I eat on!!