What could be some reasons or explanations as to the enslaving of civilians (non combatants) in war?

It's quite obvious when it comes to combatants, but what about non combatants? One interesting and fair answer I got is since women and children are likely to lose their husband in war or see him taken as a captive, there would be nobody left to support them and it would only be reasonable to also take them alongside the combatants. But what about the male civilians for example like farmers, elders etc who didn't not take part in war and that should not be killed according to many scholars. These would be able to get by on their own either way, so what could be one way to rationalize their enslavement?