Yeah, like... Look at the kind of people who become Sorcerers. Look at what it requires of you, and ask yourself if the sort of person who spends years dedicated to grasping the power of the cosmos is really going to content themselves with being some podunk king's court magician. Hell no, they're going to take the throne by right of "I command wonders, and you do not."
I mean, the Realm can keep something like a leash on its Sorcerers, but that's because the standard members of the ruling class in the Realm are Dragonblooded, not mortal dictators on the Threshold. Generally speaking, if a Sorcerer arrives in a Threshold nation, the local ruler hopes the reason the Sorcerer doesn't rule a kingdom is because their particular brand of being a Weird Creepy Pulp Spellcaster means they don't want to, because if the reason is "they haven't gotten around to yet," then this is probably them getting around to it.
The scales are somewhat different if the nation is a heavyweight with like, magical halfbloods in positions of power or ruled by an Outcaste Dragonblood, but nations like that are pretty thin on the ground.