Historical Background
Societies split into two strata following the post ice age (Neolithic) agricultural revolution. The new split, between ruling 'beneficiaries' and subservient 'workers', was made possible by the creation of food surpluses. (It did not have to be this way; more equitable distribution mechanisms could have been followed.) Thus exploited farmer labourers would feed the new warlord/landlord/emperor beneficiaries, and their ensuing dynasties. Also, workers came to be able to work on projects other than food production; that is, with increased productivity (yields per farmer), workers came to be able to produce capital goods (eg economic infrastructure) and monuments as vanity projects for their privileged masters. And, increasingly, farmer workers could support armies.