In practice it's rare that someone simultaneously can't work for someone else yet can work for some combination of customers, investors, and employees. Running a business is rarely about working in isolation, taking orders from no one, and letting the money roll in.
Many of them can work for someone else, but it would be incredibly difficult. Imagine being founding engineer at a small startup that fails, then joining a large company and having to deal with tons of bureaucracy, slow processes, and red tape. Sure, you can "do" it. You can do the work. You can follow the processes. The money is nice. But it's frustrating.
Have you been both an entrepreneur and an employee (after having been an entrepreneur)? I have. I'm pretty sure the skillsets for each are completely different.
