[toyg]

You know that stuff about the human brain being terrible at correctly calculating the odds? I think this sort of rule-making comes from that.

Maybe you'll hire a bad sheep every 20, but you'll be so scarred that you'll make a rule making 19 lives miserable, just to avoid the lone asshole taking advantage. In the same way as we think children shouldn't be left out on their own (because we read about some pedophile at the other end of the country), we then assume employees are assholes until proven otherwise. It's shitty for everyone involved, really.

[felipemnoa]

Another example is renting apartments. One bad tenant can cause a lot of harm, especially if you are a small landlord ie. three apartment house. You can go by years without a single bad tenant but all it takes is one bad one for you to start checking credit reports, references, etc.

[User23]

The lone asshole taking advantage also makes the other 19 miserable. The effect on morale is crushing. Always think past the first order consequences.

[vorpalhex]

If the lowest tier of job is relatively easily replaced, one assumes the next tier is as well meaning the people who are often making these rules are not well trained veteran managers but people who may be first time people managers or not be cut out to be a manager.

I had an early crappy hourly gig as a kid (as most do) at a major chain and in the span of my two years there we had one manager get caught doing crystal meth, another get caught flagrante delicto and a third who was just a jerk.