for all you "baby-makers"

I was reading a book recently that posed the question:
Why do people have children?
No, I'm not looking for the physics here, I get that part (man + woman = whoopee).
Rather, what are the reasons for having kids?
This book posed two reasons, and I seriously hope there are more:
1)Selfish Reason- children help us be less lonely, children give us meaning in life
2)Other Reason: to tell our story (family, God’s) and pass on our heritage for the world

Oh, and another book I'm reading says that Islam is gaining ground across the world because Muslims are having more babies, while Western Civilization families are having less. So, maybe in this light, competition (this could be important for us guys anyway) is a reason to have babies????

Help me work through this very important topic.