Why do poor people have such a strong desire to control when raising children?

Because if you treat raising children as an investment, then wealthy families see it as buying defensive long-term assets, while poor families are directly heavily investing and holding onto assets that can get trapped...
When a person has nothing else to look forward to besides heavily investing in one asset, isn't it natural to stare tightly at that single holding every day...
In the market, you need to learn to diversify risks; the same should be true in life...