Why have so many kids?

A recent question regarding unemployment/welfare reminded me of a related question: If you lacked education or formal training and had a pretty good chance of spending your entire working life near minimum wage, why would you continue to have children? I personally know quite a few people who struggle mightily and bemoan the fact that they can’t properly clothe or buy toys or get medical care or pay for college for their kids. Not because of any disabling event that occurred, but because they just aren’t fiscally successful.

If I knew that I couldn’t properly care for or support kids, I wouldn’t bring them into the world. But in the case of the three families that I’m thinking of, the smallest has three kids, the largest, six.

It’s not as if we have nuclear families anymore. We no longer produce kids to help run the farm or work in factories to bring home money. Why do people have so many kids that they can’t adequately care for? (Forgive the gross generalization, I realize this question does not apply to every poor person. And I am not promoting limiting reproductive rights. I just don’t understand why you would make that decision.)