Why are the soldiers in the ancient national army mostly the scum of the bottom of society? Like the European army, most of them are drunkards and hooligans.

This is related to the military system. General soldiers are from the bottom of society, so good people don't serve as soldiers.

The ancient military system in China refers to the ancient military service system in China. It mainly includes integration of defense and civilian technologies system, all soldiers system, conscription system, military household system, regiment training system, militia system, recruitment system, health system and Eight Banners green camp system.