Earlier quoted context omitted.
> I'm sure many of us wouldn't have been a programmer if we hadn't had access to SO/Github around 17. I'm sure many of us didn't have any access to StackOverflow and GitHub when we were around 17 years old, because StackOverflow and GitHub didn't exist yet. For several of us, git didn't exist yet. Heck, for some of us, the web didn't exist yet! Kids these days...
Many of us != most of us. What I said and what you said are not mutually exclusive.
In the 90's most teens already had access to a primitive internet where they could chat with anyone in the world using BBS[1], which was not too different from a modern social network. Email was already a thing as well for some time, but probably became widespread at this time... by the late 90's the internet was already quite similar to today for geeks, except perhaps videos (and even high resolution pics) were not a thing due to the low speed of the net.
StackOverflow and GitHub only came around in the late 2000's, which is basically yesterday. Before them, there were similar sites as well (the infamous expertsexchange for SO, and SourceFourge for GH, for example) for quite some time, but they surely became very dominant in their areas.