There's a big difference between running a mercenary company, and being a foot commander in a mercenary company.
Every noble in BattleMaster is considered to be high nobility, the cream of the crop, the people to know.
Look at it this way: The difference between the high nobility—the player characters—and the lesser nobility—part of the faceless masses of NPCs—is that no one would ever even think it possible that an NPC could be elected Ruler. Just as no one would ever think it possible that a lesser noble could be King.
