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.
I play Hattrick because I am a big football fan and I have always liked to play football manager games, like the German game "Anstoss" or "EA Football Manager". I play Hattrick since 2002, even though I had a break because of the birth of my daughter. So Hattrick has been with me for most of my life, you could almost call me "addicted” to Hattrick!
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 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 love Hattrick because it's simple. It is not taking much time to learn the dynamics, but you can tweak it forever. I love Hattrick because to me it is like Subbuteo or Risk. It is simple to learn but hard to master. It's still exciting to wait for 90 minutes to see the result of a game, four months to see the end of a season. I love Hattrick because it is possible to set goals for several years, to see your team growing up, to learn the names of the players, and to build memories about them.
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!