Because he's 14 and super stoked about accomplishing something that many people twice his age couldn't do, so he's showing off a bit.
Sometimes I'm baffled by how hard it is for seemingly intelligent people to grasp very simple human behavior. Spend an afternoon with a kid once. I promise you they'll let you know when they think they've done something cool.
> Because he's 14 and super stoked about accomplishing something that many people twice his age couldn't do
So what? Why does age matter so much? A 28 year old may have less programming experience and help from sites like MakeGamesWithUs and still complete similar projects. Why is it so important that he's 14? He obviously isn't the only 14 year old coding and completing a project, it's not even that rare anymore. Probably not as rare as a woman making iPhone app, at least. With today's technology, everybody over the age of 12 can learn programming, build apps and complete university classes.
I post my projects to HN too, I have only once reached the front page. I never mention my young age, and I won't do it here, because it doesn't matter and it's not relevant.