The camps were designed to run with a minimum of SS personnel and not so much personal contact.

Kapos were frequently employed to keep order and handle a lot of the day to day business of the camp, including punishments and physical abuse. Kapos were prisoners themselves but they earned special privileges such as better food, housing, and freedom from abuse in return for working for the SS administrators. The average SS man at a concentration camp would not really need to come into close contact with many prisoners, and thus the camps could be run with a skeleton crew of SS men with a lot of local enforcers.

The most distasteful of tasks, such as preparing and cleaning out the gas chambers was assigned to the Sonderkommando, a work unit made up of camp inmates. They were not necessarily a 'disciplinary' unit like the Kapos but were instead doing a horrid and distasteful job that put them in close contact with lots of corpses. Sonderkommando were kept apart from the rest of the inmates and also given slightly better conditions in order to keep them strong enough to work. The Sonderkommando were not as privileged as the Kapos, and would soon find themselves in the very same gas chambers they knew all too well. It would be the first job of the new 'generation' of Sonderkommando to dispose of the previous one. The Sonderkommando men 'knew too much' and so were disposed of and replaced with a new crew after a few months. Some of them managed to smuggle messages detailing the horror they witnessed and participated in out of the camps.

As you can see, much of the nitty-gritty of running a death-camp is passed down as a duty of the prisoners themselves. Refusing to work for the Nazis would certainly ensure you severe consequences. Working for them would give you a chance to possibly survive, at the cost of betraying your fellow inmates. Some people did this for pure opportunism, others were hateful anti-Semites (camps had a wide range of people, and not just Jews), while others were simply doing anything they can to survive. It is hard to judge them from afar without knowing what it is like to be cold and starving to death and to be offered a job that might improve your situation at the cost of your fellow prisoners.