There are a number of reasons I stayed.
The first was that this was the first online community I had ever joined, and I was curious about what this universe was like.
Secondly, as you have surmised, and also much to my surprise, I have made some good friends here, people whom I have never met in real life, but still enjoy a relationship of the sort that certainly approximates to friendship, and certainly compensates for the fact that many of the with whom I was friendly at school or college, are no longer around - simply different life journeys, countries, and so on.
And thirdly, I have lingered because this forum has opened windows (all puns intended) for me to different perspectives and views on life - and indeed, views on life articulated by young people - which I would otherwise not encounter.
I used be an academic, and teaching eager and questioning youngsters did help keep your own mind active and alert. Since I have moved on to other things, it is interesting (if not always agreeable) to have a forum where you encounter some whose views, mindset, and outlook differ radically from yours.
Besides, you can learn a lot here - at times.