It's bad from that PoV because slaves can't reach their productive potential as if they were free. Literacy is forbidden, they can't switch jobs and can't advan

It's bad from that PoV because slaves can't reach their productive potential as if they were free. Literacy is forbidden, they can't switch jobs and can't advance their skills beyond manual labor, their families are frequently broken up and they're subjected to tremendous physical, psychological and often sexual abuse.