For me, part of the Zakos' mindset is that they reckon that whatever happens will happen anyway, since it's not in their power to do anything against it. "Someone will hurt these people. It could be someone more cruel than me. Someone will do it and take the money. So why not me? I have bills to pay." After a while they enjoy "fighting" people who are, because they know that someone more cruel and dangeous may take over the job indeed, afraid to fight back.
The main villain knows that they know and calculates that they will not take a risk. Plus, these Zakos are cheaper than real professionals and better to control than real psychopaths. But when there is an uprising, he will gladly sacrifice them, just to buy a little time until the professionals and the psychopaths arrive. Some Zakos may see this too, but most probably develop an overconfidence that makes them continue to fight when they better run.
From "Zako Artwork" thread:Corrupt prison guards fit perfectly in my fantasy. When they finish their shift, they put the uniform into the locker, jump into their cars, return to their houses (both a little too big for a mere prison guard), their families, dogs, flower gardens. They play hockey or violin, drink beer or champaign, watch TV or go out dancing. They enjoy (or endure) an absolutely normal life, courtesy of the money they get for ruining that of, for example, political prisoners.
