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.
I play Hattrick because it has become a sort of strange family to me. I've been playing since 2008 and I've met a lot of people here. Very interesting people, very strange people, all kinds of people. I think I'm still playing Hattrick because in this game I have found a lot of friends. Some of them are now very close to me and my family, they have seen my child's birth and Hattrick is still the place where I can find them.
The Hattrick community is colourful, it really helps expand the Hattrick world. You can find plenty of helpful managers that can help you with Hattrick and real life questions.
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!
One of the best parts of Hattrick, for me, is the fact that you can somehow massively relate to a bunch of fictional players with fictional names and treat them like they're real world players.
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.