It's because we've all been tricked by the Judeo-Christian Complex, to not control their birth. For instance, birth control has been severely ripped apart by the Catholic church. The reason... We needed lot's of workers to build our towns, and railroads. So the more uneducated Hispanic children out there, the better.
The same can be said for sex before marriage. Men are attracted to virgins, a girl who had sex before marriage, wasn't as priceless, as a girl who hadn't lost her virginity, and didn't command the dowry her father was after, as a trade for giving away his daughter. So not only was it frowned upon by man, they decided to make it a sin against god.
People need to plan having children, they don't and America is churning out generations of idiots. If you can't afford to give your child a better life than you had, you have no place having them.