That is most certainly not the case. You can very well be a merchant en route towards Praeclaran space for whatever reason or getting in trouble within Lucky 7 itself, for instance. Or a travelling space musician or just an asteroid miner with a crappy life who gets drafted into space shenanigans because he can really swing that plasma pickaxe. You just insert "space" in front of an occupation, tech up the required gear if necessary and you have a space job. A space anarchist trying to tear down the Praeclaran regime would also work.