Historically, companionship and sharing resources have seldom been the sole occupations of marriage. Folks breed.
In preindustrial times, child labor was a considerable convenience to their charges, as the little ones could help with the chores. At the turn of the 19th century the average American family included 8 children.
With industrialization offspring increasingly became a financial burden. By the 21st century it cost over $200,000 to rear 1 child in the United States, including college.
Economic imperatives spelled a decline in parental care among the general population in industrialized nations. As couples struggle for a comfortable standard of living, child-rearing represents yet another time burden, on top of the financial drain. Though parents wished to spend more time with their young, financial considerations limited their commitment. Children who fend for themselves after school – latchkey kids – became a common phenomenon.