You make an excellent point. Being a parent isn't for everyone. And most generations of people became parents for the exact reasons you stated. That doesn't mean they didn't love their children, but their actions came from self-interest. Arranged marriages, indentured servitude, and child labor of the past prove that.
People who raise children and do a good job deserve commendation and support, but that doesn't mean that everyone should do it.
According to the Free Market rules, raising of children should be done where it is cheapest. In other words:
The Law of Comparative Advantage dictates that "Americans should not have children!"