AbdulAlhazred
Legend
You could use Ancient Egpyt as an example, all of the kings and pharaohs were warriors, it was a central part of their identity. From Narmer, the first king who united Upper and Lower Egypt (or Aha, if you prefer) through the Senwosrets of the Middle Kingdom, the Thutmossids of the New, and the Ramsses of the Late Kingdom, all were warrior-kings. Even if much of their wall engravings were exaggeration (Looking at you Ramsses II) being a warrior was a key part of their identity.
'warrior', yes, but how many of these people actually personally engaged in combat? Their main attributes, as far as I know, were as God-Kings. Some had great reputations as generals, and obviously in an age when power was acquired only by force being a great general was pretty much mandatory if you were going to build a new dynasty. I could still represent any of these people with 0-level stat blocks.
As for the Greek 'Kings', the evidence is that 'King' is an anachronistic concept that we have placed on them. They were warriors in a time and place when war was a sort of tribal affair that involved a lot of personal combat. Were they heads of state or rulers in a modern sense? No, probably not. In any case the plains of Troy were host to MANY figures, and probably few of them were really extraordinary warriors that need to be anything beyond 0-level man-at-arms rules-wise. And again, nobody says that higher level figures don't exist, the question is does class form some sort of iron-clad law that they're locked into, or is it just a DM convenience at most?
I'd also note that many different attributes are assigned to different heroes in the Illiad, and not all of them appear to be straight up fighters at all. So its not clear to me that class would represent them all very well anyway.