I would say the community is the strongest reason I have stayed in Hattrick for so long. The game too of course. After having trained my players and played in the French Division 2 for a while, I started focusing on training international players to help the Moroccan team. Today 80% of the defense of the Atlas Lions was trained by me!
My best Hattrick memory was when the city where I lived (L'Aquila, Italy) was hit by an earthquake. I received a lot of support, a lot of help, a lot of love. It was a very hard time and Hattrick was there, with its community, with me. I will never forget that.
First I played Hattrick to win, but over the years, I came to realize that reaching the absolute top wasn't going to happen for me - I'd need to spend too much time to fully understand the game and make use of that knowledge. So I stuck around because of the great atmosphere and people in the forums. Recently my interest in the game itself increased again, which made me open a team in a new league (Botswana), and I'm trying to be at least semi-competitive there.
What I like about the Hattrick community is that there are real people and you don't just compete against the computers. You play against each other, but you can also help each other in the forum and talk about everything.
I like that Hattrick is a slow game. Here, I have time to think everything over. I also appreciate that Hattrick gives everybody the chance to be the best because you can't buy in-game advantages.
I am one of the old users who likes to do my own research to learn how the game works. I like that this is a thing in Hattrick. Not everything should be mentioned in the rules. I also like the federations where you can have some real tight friendships. More than some friends call Hattrick a forum, with a soccer-game attached to it.