And that ability to "handle having a baby" isn't just about "maturity" but also about where you are in terms of finances and your career/education? And what about people who could take care of kids but just don't want one? Should they never be allowed to have PIV sex ever?
I think you're being a tad narrow-minded. Oftentimes, maturity shows itself by being realistic about your situation, and waiting until the point when you feel you can give your child the best quality of life, rather than just feeling like you HAVE to have the baby because it's your punishment for screwing up. Parenting should not be a "punishment"; this is the reason we have so many neglected and unloved children in this world. It should be something that people happily choose, when they are ready.
Also, we have birth control methods out there that are 98-99% effective when used correctly. It's ridiculous to act like babies are an automatic conclusion you need to be prepared for even when you're talking only about the types of sex that might result in them. The likelihood of getting in an accident when you get in your car is probably higher than getting pregnant if you're using the pill and/or a condom correctly, but no one acts like every time you ride a car you are potentially gambling with your life.