The classic view of the state was that it represented a people. It's function was to represent and protect the interests of a people.
Therefore, the state was responsible for protecting the people from enemies and invaders, the integrity of the borders, and the general welfare of the people. There are 3 basic ways to eliminate a people - annihilation, infiltration and dilution, and finally, infertility. So, the state, along with it's general function of protecting life, limb and societal cohesion, has a corollary function of promoting the continued production of the people it represents.
When you get into the modern view of the state as simply a geographical monopoly, it's interest in promoting the continuation of any people becomes a little murkier, but is still there. After all, it's difficult for a state to continue when none of the people believe in the ideals it espouses. So therefore the state must encourage the production of the people that do believe it's organizing principles.
