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.
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!
I started playing Hattrick in the summer of 2002 when a friend, who I played "Fantasy Wrestling" with online, told me about Hattrick. I made many mistakes in the beginning. At that time there was no such thing as mentors or beginners' guides. So my very first club was bankrupt after only a few weeks. Luckily, I was able to restart with a new club shortly after that and then I did a lot better.
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.
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.