Everyone assumes the inability in that saying comes from ineptitude.
A less popular possibility is there is too much change to make in the world, so teaching others is the path to bigger impact.
That’s the same mechanism of how a job is created, an owner, or shareholder, or manager, or executive with too much to do, seeks to teach an employee how to do the tasks he wants to offload. Repeat that enough times down the line and that is a company.
Of course, some owners, shareholders, managers, and executives are better teachers than others, but nonetheless teaching is making an impact. A bigger impact.