The process of evaluating the people that make up the organization should be under constant improvement though, and again, simply because of dealing with large numbers, there might be a few false positives, but on the whole as an organization, management should be on the lookout for who isn't performing.

Like most things in life you need to strike a balance. Most managers hate firing people, even when they probably should. The person might be just the kindest sweetest person they know and maybe a friend but they're just not very good at their job. A big overall workforce cut gives them the excuse to fire the person without having to hurt feelings or look bad.