Humans were created by ancient alien gods and so the extra intelligence we have is given to us for a purpose, the purpose is to migrate to the stars, spread in the universe etc etc... So for all that we have to have kids. Animals cannot move to other planets/stars, but man can, then man can take animals with it as well... Humans rule earth, it is a responsibility, not a random fluke which should be throw away.
Secondly, having kids is the greatest joy on earth, creating a human life inside you, women often say that creating a life inside is the most special feeling they've had, you think it is nonsense ? Plus when people have kids, they hold the kid in their hands and feel satisfied, happy, even selfish people become selfless when it comes to children.... why is that ? It is what is natural.
What good are hospitals if we don't have kids born in it ? What good is building a school if no kids to teach there? What good are academic patents? Somebody else would also discover/invent those patents if we don't, is that a big deal ? All these things only have relevance if humans procreate.
See if someone cannot reproduce due to birth defects or some health issues then it can be considered as the will of God ..... no worries.... but if we have a gift and we don't wish to explore it, then what is our purpose on this earth ? Elon Musk's dad says that only reason why humans are on this earth is to procreate, he is right in some way you know.
Yes society gives us freedom to do anything,nobody will arrest us if we dont have kids or marry, but end of the day if we have a gift (we are fertile) and we choose to waste it then it means we are living an aimless life with no contribution on the cosmic scale...