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 Hattrick is that there are not 248 925 784 skills that you have to pay attention to. I like that there are several (but not too many) tactics and that they all have weak points that other strategies can beat. I like that this is a slow game, it fits my private life. And that is probably also why I still find it interesting after almost fifteen years.
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!
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.
One reason I play Hattrick is because I like the cyclical nature of the game. You start with an idea about what kind of team you want to build, then you train long-term (up to 3 years in real life!). While you build, you can test and try to comprehend the aspect of the match simulation that you want to master. I also like the tactical choices you have to make for each match. But the most important component is the community.
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!