This question is more about social status, demons have a hierarchy and they have slavery in the abyss. They will often fight each other for little reason, so why don’t demons ever just go to Astlan abduct a few somewhat attractive mortals and breed them to be their eternal slaves? They hate them to begin with and it gives them a group with a social standing below a rank 1. It sounds like something they would all agree to so why hasn’t it ever happened?