Mostly because:reanjr said:This all mounts down to the question of why the PCs don't kill all the 10th level aritocrat kings and topple the kingdoms.
a) They're not evil
b) There are laws against this
Neither of this prevents them from doing it in the Abyss. And it even often happens on prime material world when some bandits ride into a remote border village, slay the officials of the town and set themselves as the new rulers (usually leading to an adventure for the PCs to drive them out)