It ought to be obvious and universally accepted. A subordinate is one under authority. Sadly, in today's society with its emphasis on self, rights, democracy and independence, obedience may seem archaic and outdated to many people. Some employees expect their supervisors to merely suggest tasks, giving them the option to accept or decline. When employees persistently disobey, even in small ways, they usually soon lose their jobs.
Authority tends to get a bad rap.
Abuse of authority is bad, but authority is neutral. When used in a sensible way for constructive purposes, it's invaluable and good. Leadership is essential to success. And success is good for everyone, employers and employees alike. Understanding all this makes authority easier to obey.