Children are the basis of posterity. Without children you cannot have posterity of any kind regardless of whether it's environmental, financial, moral, religious, cultural, racial or other. Societies with low birth rates don't control the future. And societies that are transitioning to low birth rates gradually lose their culture and sense of community. Under such a society all roles cease to exist, including gender roles, which become completely androgynous. There's no future to live for in such a society and therefore a destructive nihilistic boredom sets in. These societies are parasitic, live off the fat of prior generations and are all doomed to extinction.
Children of Men is a sci-fi film that shows the most extreme scenario of a low birth rates - a zero birth rate society. Available on netflix.