If you have a bunch of people working well together, ranking them poisons the entire working relationship. With an absence of outside influences, top performers will seek each other out and group together. So, any "bell curve" would be skewed to the point that it is meaningless. The person at the bottom of the ranking in one of these groups would be the top person in most other groups.
If the hiring is done right, you don't have poor performers. And the few that sneak in are quickly identified. The key is to put the hiring decision into the hands of the people that will be working with the new employee. If you let HR make the decision, then they start filling "quotas", and you get people that can't make the grade.
HR is a poison unto itself which has risen primarily because of government regulations and oversight, i.e. "quotas", and lawyers and unions, i.e. "discrimination" lawsuits.
Very often, the very people who are hired into and staff these economically useless HR positions are chosen because they are the very target groups meant to benefit from those skewed policies and not because they add any particular value to the company. They therefore perpetuate the poisonous system of embedded discrimination and mediocrity with a vengeance.
The HR Department is a millstone around the neck of any company who has one.