This was because it was believed that since they were young they'd have the strength to work more than older women, and they were unmarried because it was believed that then they could focus and give their all on their job because they wouldn't have a family to take care of.
it was more then likely unmarried women because back then they believe women was created to take care of men so if you dont have a man to take care of your put into labor to take care of the men in the military. btw i just done the mastery test on plato got a 100
