It gives me a chance to learn new things, and at the same time, a chance to share things I know, with people who don't.
Also, it gives me a chance to interact with real people in a fun way, even if I'm just sitting at home alone.
The addictive aspect of it, comes from the points system. I've been playing video games all my life, and most video games keep track of your SCORE. So the fact that this system keeps a score, compels me to keep participating more and more to try climbing as far as I can on the leaderboard. Right now I'm still new, so I don't have a lot of points yet. But I admire all of the really smart people, who have been doing this for longer than me, and who have a lot of points.
It also gives a real life scope of how real people ARE, and how they THINK, in an imperfect world. Sometimes, I see people who ask questions which are just RIDICULOUS. Some of them make a lot of typos, some of them ask questions to which the answer seems so obvious that I can't help but to think they already KNOW the answers. Sometimes I can help people with their relationships. Some people are just GOOFY. Some people are cool, and make good friends to email. Other people are shy and don't ALLOW email contact (the options to CHOSE those features (or not) are great). Some people are controversial, and they ask questions which might irritate other people, causing their question to get reported and/or deleted... But at the end of the day, I figure, that's just humans being HUMAN. So in that aspect, it provides a very REALISTIC and educational view of what people in society are really LIKE, without even leaving my apartment.