Story isn't grabbing me that much. "evil empire does EEEEEEEEEEEEEEEEEEEVIL things for 0 reason"
Dude: "hey you know how human labour is extremely inefficient and resource intensive"
Dude 2: "yea"
Dude: "let's make labour that can't use tools so they're even more inefficient"
Dude 2: "but why"
Dude: "well they need slightly less food so we save there rather than trying to create an efficient operation"
Dude 2: "whew it's a good thing we're not a high-tech sci-fi empire that can create efficient digging tools"