Well, I'm employed by the Hokage or the leader of our village, but, they're generally known for their undying love for the village. Those selected to be successors are usually evaluated based on dedication, skill, and desire to love and protect the citizens of Konoha. It's the Hokage's duty to serve the village, just like how it's our duty to serve both. For example, Lady Tsunade, the current Hokage, gave all of her chakra to heal thousands of people during an invasion which caused her to fall into a comatose state. That courageous display of affection, love and the willingness to protect isn't special for the Hokage, it's an obligation, which is why very few have potential of becoming one.