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.
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.
My biggest achievement in Hattrick so far is that I have won some titles with my second team in Bahrain and reached the semifinals of the National Cup in Italy, but I hope, a few months from now, that it will be winning the World Cup for the Italian NT.
When I registered, I liked that Hattrick has fantasy names instead of real players. That got me hooked. I also liked that all opponents were people of flesh and blood… and also that they turned out to be really helpful, showing me the steps you need to take as a new user to improve your team. Today, I am a good mentor myself.
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!
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.