Getting pregnant is natural and easy. As die_sekte points out elsewhere on the page:
(a) Sex is cheap, good entertainment. (b) If you are already poor, children aren't going to make it any worse. (c) For some reason, most people really want to have children. (d) Humans aren't exactly rational creatures.
And I'll add to that: when you're poor and poorly educated, you neither know much about contraceptives nor can you afford them. Hell, in the US we have a lot of kids who are perfectly well off and don't know how condoms work, because of various kinds of screwed-up politics. If you're poor? You might not even know you have a choice in the matter. And "abstinence only" doesn't work.
I find it very hard to believe that a significant part of the US population doesn't know enough about condoms or pills. The problem is that a large percentage of people don't use contraceptive methods and have kids out of wedlock.
I don't know for sure but it sounds like kids happened when there were two people, and then a partner took off. If all you can act on is that this person promises to be around to help you pay for and look after your (theirs too!) kids, and they break that promise.. what can you do? never trust anyone? It's just not quite that simple, though I absolutely agree with the sentiment.
Daniel Markham here said you're never ready to have kids ( http://news.ycombinator.com/item?id=1474454 ), but I strongly agree with the statement that you should be able to afford kids before having them.
In the sense that yeah, just like there's no good time to get married, there's no good time to have kids, since life just gets in the way.
That said, I think at a young age, like in your teens (and nowadays in your early 20's), there's still a lot of things that you need to do in order to make your childrearing easier.
If you don't get to that point, you're always trying to do short-term gains to raise your kid, while not being able to invest (either financially, educationally, or situationally) in long-term gains.
