The first explanation that comes to mind for me is that perhaps it's because executives often own all or part of the company(ies) they run. They *pay* their employees, but they *compensate* themselves, the difference being that the draw that an executive takes is often just necessary living expenses and bonuses as needed; the work that an executive does is--ostensibly, at least--aimed toward increasing the profitability of the company, whereas an employee is--generally, at least--working just to get paid.