Cerebral Paladin
First Post
The funny thing is that even when you consider the full varieties that a fantasy world allows it still does make the most sense that most Kings are fighters.
I'm curious why you think so--I tend to think that fighters are among the weakest classes/archetypes for monarchs. They're probably quite common among 1st generation monarchs, but for hereditary monarchs, there are many other classes/archetypes that seem stronger to me.
When I think about the tasks that a monarch needs to do to rule well, my conclusion is that overwhelmingly the tasks are tasks of judgment, politics, social interaction, and policy. In D&D terms, they're tasks that call on Charisma, Wisdom, to a lesser degree Intelligence, and the associated skills (Diplomacy, Bluff, Insight/Sense Motive, Knowledge skills or the equivalent). So that suggests that strong ruler classes include bards, clerics, warlords in 4e (or marshals in 3), and the like. (It's not coincidental that the 4e classes that are well-suited to be monarchs tend to fill the Leader role.) They have the right skill lists, the right attributes, and so forth.
When I compare them to fighters, fighters have a few advantages--they're harder to assassinate (although typically more vulnerable to mind control/suggestion/etc.), they can do some of the athlete style impressing people by winning tournaments and the like (Henry VIII was a major participant in jousting tournaments, and his prowess apparently added to his stature as a prince and later king), and in a war they're well suited to wading into the front of the combat and fighting people hand-to-hand. But... even in the case of a war, it's much more important that the king be good at strategy (i.e. Int-based stuff) and at motivating, leading, and securing the loyalty of his nobles, allies, and followers (i.e. Cha-based stuff), than it is that the King get in the thick of it. And it's not like the other classes (or the fantasy archetypes that they're based on) are worthless in battles. Even within the family of fighter-types, paladins and rangers probably both make better kings: they have many of the advantages that fighters bring, but they tend to be better at the non-combat roles of a king than fighters.
I'm not saying that fighter should be a rare class among rulers. It's perfectly reasonable to believe that many prospective monarchs would be raised to be fighters, especially if you assume that first-generation monarchs (and hence the parents, grandparents, etc. of later generation monarchs) are disproportionately fighters. And certainly a monarch can be both a fighter and a great monarch, especially with exceptionally good ability scores overall. I'm just saying that as I think about it, the best (i.e. most effective) monarchs are probably disproportionately not fighters.