I worked in the telecom business. There is a measure called service level. It has been a standard for decades. Billions of telephone calls have been measured against it.
How did it come about?
The engineers who installed the first system had to enter a default. So they stuck in a variation of the Pareto ratio. And for about the past forty years, the staffing of call centers have been calculated to a standard not based on any reality. And it hasn’t changed much to this day.
This may be an Urban Legend, but when the outfit I worked for years ago was installing an Automatic Storage and Retrieval System, the reps told this one.
At General Motors (or some BIG car manufacturer), the ASRS people ran into automobile blueprints where the car was split down the middle, with positive numbers on the right side and negatives on the left. They asked the auto engineers why and got the standard "it always been done like that" answer.
It took some digging, but they said that they found a drawing where the division started with the horse and cart. The horse was negative, the cart was positive with the dividing line being the beginning of the cart.