On the topic of short Steam IDs, I probably got onto the platform for Counter-Strike, which makes sense because that's more or less the plan behind Steam. My memory of the internet back then is pretty patchy, there was some game launching site or program that had little images of rockets next to each server, no idea what it was called, but that was how some of us launched it before the Steam beta. I certainly remember spending a lot of time on GameSpy Arcade, which had several games, and a functioning friends list (a feature that Steam struggled with for a long time).
I imagine a lot of the original users are busy with careers now, but you still find some of the low ID's in places like Counter-Strike: Global Offensive, which makes sense because they must have been fans of the original mod...
Someone I knew had a story about bumping into STEAM_1:0:7 in a CSGO match in 2015. I imagine a lot of people came back to CS at the time as the skins scene was a boon to it, along with betting and the competitive matches being streamed in high quality.
I know I'm making low Steam ID's sound like they're far more important than they are. There's obviously bigger things going on, but it's one of those little trivial things that has a semi-interesting story behind it that can distract you from the current state of the world.