Those people who were tasked with observing or doing more to them were just examples of the power that could be wielded by Cerberus if it wished to use that power for personal matters.
Anyone who had been a part of the tasks would know that they would not want to be on the wrong side of them, as the target of those who would be assigned to go after them.
It would be almost like them being a hunter for so long and then having everything turn around as they would be labelled as prey for all of the other hunters to hunt.
If they were exposed to such things and knew of the things that could happen, then they would think twice before doing anything foolish that could result in such a thing happening to them.
Other things could happen suddenly, like a death or injury during a task, so that could always make it far more difficult to pay things back, and the usefulness of those people would drop as a result of such a situation if they were able to live.
