The peter principle is alive and well. When an employee is good at what they do, you turn them into a manager to oversee other people who do what they used to do - even if they are not cut out to be a manager. The fact that kelly sho and steve tidellus can identify a handful of cases where career success is not tied to promotion into management, well, those are exceptions that prove the rule. Like our friend katy johnson, the data scientist we met earlier, i didn't see that there was another path whereby i could be direct to level, but nor have direct reports.