We love and respect God and God said be fruitful and multiply. God also said that life is a gift. Therefore, we have children.
That is a fairly simple and straightforward reason that even the simple amongst us can comprehend. The first five words are simple but the agreement to the statement comes from being raised as a Christian. It may take many years of church and learning to appreciate and agree with that beginning foundational statement. After that, the reason for having children is self-evident.
In addition to the basic reasoning, people have also had many biological, economic, security and cultural reasons for having children. These can be easily teased out and we won’t build the full case here. Briefly, there is a natural biologic sex drive that before modern contraception would naturally lead to children. Children in agrarian societies were obviously useful for their labor. Large families also provided a retirement safety net. The logical reasons go on and on.
In a modern society with contraception, welfare payments and social security payments, the secular reasons for having children are without logical merit. In addition the secular selfishness trumps any emotional need that children provide. Finally, the secular man will evolve past the need to pro create and will out source that to the state.
The secular modern person will be hard pressed to provide as simple and cogent a reason to have children as we provided in the opening statement. Thus we see in reality the demographic destruction taking place in secular Europe and secular Russia and secular China.