Even if the reasons behind a traditional behavior may no longer be present, the behavior can last without anyone understanding why.
There's a a business school story that goes something like this:
You put 5 monkeys in a cage with a ladder. At the top of the ladder is a bunch of bananas, but get this: the ladder is rigged with a pressure sensor, and the floor is electrified (note) and when a monkey steps on the top rung, the rest of the monkeys get zapped.
Pretty quickly, the monkeys learned not to walk on the ladder.
Then (the story goes) the researchers swapped out a monkey, Immediately, the new monkey went for the ladder, and the rest of the monkeys ran over and beat the new monkey!
Then they replaced the rest of the monkeys, one by one, until none of the original monkeys remained.
If you added yet another monkey, it would go to the ladder, and all the monkeys would beat it up.
This is true even after the researchers disconnected the sensors.
But if that monkey had asked why it was getting attacked for going for a banana, it wouldn't have gotten a satisfying answer: "That's just the way we do things around here."
So the moral of the story is that in business, you need a new person to come in and question things, or we all slowly get used to things that don't make sense.
Note: later version of this story, out of kindness to the hypothetical monkeys, have included showerheads instead of an electrified floor. Now the monkeys all get a nice, harmless bath.