I feel like it's more about distribution of responsibility. If you have a king, he's either a good king and runs things well, or a bad king and runs things poorly. A King's success is generally measured by the quality of his kingdom, which is at least somewhat tied to the wellbeing of subjects.

In a corporation, even if you have a comparitively "good" CEO, he's still answerable to the shareholders, and thus obligated to raise the stock value by any means necessary, a factor which is not necessarily dependent on the wellbeing of his employees.