Well, for every Alteil account you get a corresponding forum account, also lots of people probably make accounts play once and leave. Usually active forum members are a small fraction of total user base.
And don't forget the people who are lurking in the forums. If you look at the replies:views ratio, the amount of views is much higher than the amount of posts. Some people (like me) just like to read the posts or don't have anything to add what hasn't already been said.