And you are wrong about why the state supports marriage. That may be a minor reason, but it is not the main reason, at least not in these modern times. We do not live in the 1600s, the 1800s, nor even the 1950s. Many marriages do not include children, and this is more and more true every generation. Marriage serves many purposes and it is a right even to those who cannot have children.
"A woman is like a teabag, you never know how strong she is until she gets in hot water." - Eleanor Roosevelt
Keep your religion out of other people's marriages.