Because when I first found the forum I thought it was a fun, exciting place. Made an account, hung around in Forum Games, The Tavern, Video Games, and dabbled in the Media forum. Now I just do a short sweep of the first page of Video Games and Tavern before heading back to Kongregate.
I joined Armor Games because of the three things mentioned in the original post, actually. The Forum seemed like a good place. Plus, it also seemed like the community is not that bad. (I have been to forums where it seemed like 8-year olds were in control.) I play lots of games on here. Since I play so many games on here, I might as well make an account. The ability to keep game data was also nice (and very useful). Recently, my computer/laptop/box became infected with loads of viruses. I took it to a computer technician and he removed the viruses, but he removed some of my data during the process. This included my gaming data. (I'm sure it wasn't intentional.)
I made mine because A) Online saving for some games, and B) I'm on here a lot.
I created my account because I like playing flash games, and I enjoy chatting on forums.
I joined AG, because it has a lot of games I could play. I quickly got bored of the games, so I sometimes post in the forums.
I really wanted to rate and comment on the games I played which is why I first made an account. After that, I came to love AG more as I made friends from around the world while talking about random things; and then the whole climbing in rank thing was pretty nice too. And all that is why I still come back.