China historically has been extremely determined to avoid fracturing into smaller states, especially since the fall of the yuan Chinese governments have made a point of maintaining sovereign integrity of China proper.
If they can't be directly controlled by the central government there's no guarantee than a crafty merchant or military officer won't try to carve out his own kingdom and maybe even become an enemy of the empire.
Yes, very true in the old days when a communication message would take up to a month to reach it is destination, and even harder to move around troops.
But with modern technology of instant communication and fast transportation, this will solves the problem, but I don't know if the ancient Chinese had instant wireless transmit technology or steam engine trains will be wanting to conquer Europe.