The 8 Monkeys
Put eight monkeys in a room. In the middle of the room is a ladder, leading to a bunch of bananas hanging from a hook on the ceiling.
Each time a monkey tries to climb the ladder, all the monkeys are sprayed with ice water, which makes them miserable. Soon enough, whenever a monkey attempts to climb the ladder, all of the other monkeys, not wanting to be sprayed, set upon him and beat him up. Soon, none of the eight monkeys ever attempts to climb the ladder.
One of the original monkeys is then removed, and a new monkey is put in the room. Seeing the bananas and the ladder, he wonders why none of the other monkeys are doing the obvious. But undaunted, he immediately begins to climb the ladder.
All the other monkeys fall upon him and beat him silly. He has no idea why.
However, he no longer attempts to climb the ladder.
A second original monkey is removed and replaced. The newcomer again attempts to climb the ladder, but all the other monkeys hammer the crap out of him.
This includes the previous new monkey, who, grateful that he's not on the receiving end this time, participates in the beating because all the other monkeys are doing it. However, he has no idea why he's attacking the new monkey.
One by one, all the original monkeys are replaced. Eight new monkeys are now in the room. None of them have ever been sprayed by ice water. None of them attempt to climb the ladder. All of them will enthusiastically beat up any new monkey who tries, without having any idea why.
And that is how most companies' policies get established.