Freeloaders aren't gonna organize and do middle of the night surgical strike raids like this but there's got to be an incentive for the people who are able.

Also, it's a lesson for smaller holdings when things get tough. You will be a target if you appear negligent in watching over your resources.

Edit: I'm reminded of that movie "Deadly Harvest" where black marketeers would make raids into the countryside to steal livestock and whatever they could find.