Weirdly, age is only discrimination if they're over 40 in the US, while below that you can do as much "illegal discrimination" as you want, which is pretty messed up.
Hmmm.
By the way, I started coding at the age of 13.
The extra years of experience in Delphi, C#, JavaScript, HTML, CSS, PHP, Python, Ruby (before Rails even :-) that I had before the age of 18 are certainly a significant part of why I'm ahead both in seniority and pay of many people who work side-by-side to me, or for me.
For the record, I did paid screwing-around-with-computers from 15 on, but the unpaid stuff added at least as much value to me as an employee.
Ditto my abandoned humanities degree, which I also don't put on my résumé. More valuable to my work as a software developer than the CS degree I eventually got. I wouldn't present it that way for obvious reasons, but that doesn't change the reality of it.
It's not equivalent: when I got my first job at 19 I was incredibly naive, I'd barely used source control, and I had a bad case of NIH syndrome. BUT, it's given me a depth of experience that is rarely matched by my people in age group.
Actual professional experience is often quite routine, and time pressured. You don't get the same opportunity to experiment and learn things in depth that one has as a teenager. It might not be the most efficient way to learn, but it's certainly effective.
Do I sometimes feel a bit of a fraud putting "12 years of experience" on my CV? Yes. But I also know I can hold my own in a room of people who have 12 years of "real" professional experience, and that it was this early experience that enables me to do that. So it seems equally disingenuous to not put it on my CV.
For an NFL player, running speed is clearly a BFOQ. For Hooters the case is more complicated (IIRC there is case law)