While starting early is obviously a tremendous advantage, it's a shame that it's often discussed in such an exclusive way.
For reference, I am a female programmer who got a /relatively/ late start. I took my first cs class because I was embarrassed that I used my computer like an Internet Explorer box. Barely three years later, here I am knee-deep in code with a job offer from Google. Am I an exceptional hacker? No. Can I hold my own with the 'started-at-12' crowd? Pretty much.
It saddens me that more people don't feel empowered to dive into a new field. Many people, especially high-achieving students, suffer from the misconception that to succeed in various technical fields, you must specialize early. Whenever an outsider expresses any interest in programming or math, I encourage them to try it. "It's too late for me," and "I'm just not an X person," are common responses. These attitudes are caused in part by the way we STEM folks don't bother as much with non-children. You might tell a little kid about how cool programming is, but do you even attempt a real explanation of your work with a young adult? Your uncle? If so, gold star. If not, you are only contributing to the wall between the tech-savvy and general populace. It's never too late for someone to learn.
Too much stress on the early start just adds another barrier to entry for people like myself who lacked either the exposure or awareness to get started sooner.
If our goal is to make the tech universe more accessible, we shouldn't be perpetuating the idea that you need a certain background to participate or excel.