There isnt that much difference really, its only a few years. And what do most people do in those few years? Either work or University, and a hell of a lot of partying. Plus having kids makes you grow up pretty fast anyway, you usually have no choice.
It would have made a huge difference to me. At 16 I had never kissed, never dated, refused to consider the possibility of love, let alone commitment. I lived with my parents and hadn't even held a part-time job. My main concerns in the outside world were finding other people I could communicate with and not making an ass of myself in high school.
I still wasn't ready to have a kid at 20, but I was closer. I lived on my own (rent paid by others), had been freelancing for three years, covered my own food and other expenses. I was in a 3-year committed relationship and sexually experienced. I didn't party.
Money sense can also have little to do with age. One of my friends started doing his parents' taxes and handling their finances when he was thirteen. Now in his mid twenties he has enough saved to consider buying a house, while one of his parents has trouble with the bills (on a 6-figure income!) and the other still relies on his management.