First of all, I think its because what everyone has already stated, lack of advertising.
The few players who do find the game through friends, etc, find the game slow and boring (because lets face it, the first few days are slow, and boring). They don't know what farming is, and think this game is just build something new in your HQ every few hours.
And there is such a big skill gap between the new players and experienced players, that the few new players who found the game are usually made farms by the more experienced players, and end up quitting.
Meh, my two cents :s