A few reasons and comments to have children
1) fulfilling life
I think having children has the potential to produce a more fulfilling life for myself than not having them, although I certainly believe a fulfilling life is possible without children. The increasing marginal utility from interactions with children and a loving family could have a tremendously rewarding lifelong influence. Just as sharing a positive experience with a loving partner produces a more enjoyable life so too I think sharing a positive experience with a loving family and children can produce a more enjoyable life than without.
2) programming a supercomputer
I find the growth and development process of children absolutely fascinating. Watching thier intellectual development as they learn to grasp objects and then later grasp more complex concepts is incredible. Every human brain is like a supercomputer and having children gives you one of your very own that you have tremendous programming influence over!
3) changing the world
A lot of prospective parents decry the terrible world as one no one would want to bring children into. Obviously we don’t think this of the world as it’s better than its ever been, but even if it wasn’t, why would leaving it to the fools and decrepit be the way to go?
4) save your life
In the near term, an intelligent child raised to rational and productive parents may very well contribute to your material well being in such a way as to save your life. Certainly pets will never do this. In the long term, generations later, a society of immortal intelligent life loving people may one day discover a way to go back in time and revive lost loved one. Unlikely, but more likely than if the world were left to life hating luddite mystics.
5) take care of you when you are sick / old
As we age and weaken a loving family will be there to help you through the most difficult times in life, take care of you when you are old or give you strength in difficult times.
6) wealthy family pyramid
Personally I think children should financially reward their parents for bringing them into the world and make sure their lives are comfortable and financially secured. Our parents spent enormous time and money ensuring we would have the chance for more successful lives and one day I hope to be able to properly reward my parents for doing so, and I wish I could have perpetually done so by sharing a portion of my income with them, hoping they could have retired early. Sadly the current economic climate makes this impossible for me. All too often children are financial drains on their parents even into adult hood, most often when they were raised to find the avoidance of physical or mental effort to be the purpose of life, instead of productive self rewarding achievements. I like to think of the D’Anconia family in Atlas Shrugged, where each was expected to exceed the previous generations wealth. Maybe not necessarily financially, but in some semse, either materially or philosophically. Such a practice would likely see the rebirth of family dynasties.
I also think some of the disadvantages often portrayed to having children are overblown. Raising children need not be as expensive as everyone suggests because the excessive coddling and spoiling is not necessary or psychologically healthy. Teaching children from a young age the foundation for a healthy and rational sense of self worth should (theoretical) reduce the desire of theirs to be the most fashionable or most trendy and to avoid the less rational career endeavors with a focus on more rational and productive careers which include more rational educational strategies which might not include blowing money on the most expensive most prestigious school that offers no better education than a moderately expensive quality school.