The conveyor belts are made of fragile cloth that frays easily, especially the longer they run. At any moment the cloth may separate, sending the shell and its inner being plummeting out of sight. Eventually, all belts fail.
However, there is a golden lifeline running above each belt. It would be useless to the soft souls trapped inside the hard shell of human nature, but once upon a time a Man came down that line and punched a hole in the top of each shell. Now the soft souls can see the lifeline, if they choose to look up. And if they choose, they can reach up through this hole to grab on to the lifeline.