Responses
Idk about the actual reason. So this is just my guess.
If nobles do not put their name to their store it means whatever happen to the store will be not their responsibility.
While the nobles gain wealth from there, if something happen to the store (like being spies or such) they can say they don't know anything. They didn't have actual evidence to be included. And this nobles can also evade profit-tax from the said store because its not theirs.
From a kingdom/empire viewpoint, thus acts will be an illegal/law-breaking or even seen as treason..
So his point is??