There are no morale/loyalty/control penalties for having no lord. If the entire region is empty, then only 50% of the tax gold will be collected, and it will all go to the duke. And, none of the food will be sold-if it's a badlands region, that might not be a problem, but if it's a major food producer then you will have a problem.
And, if the taxes are too high, causing unrest, then there's nobody to lower them. Nobody to build recruitment centers...you get the idea.
