The game is designed with the explicit expectation and intention that nobles will belong to realms as the default. It is not desirable to make it easier to be a random rogue running around.
If you want to play a lone wolf or ronin samurai, then your options are a) play an adventurer, b) belong to a realm and do stuff on your own as long as they'll let you, or c) go play Dark Souls or something, because BattleMaster is a team game.
