For me there are two reasons.
One is that devs of the game don't visit the forum to give any extra info or have some on-line communication with the players
the other is that the forum is hidden.
If someone playing the game with fb, he can't see the forum.
The fb of T11 also doesn't promote at all the forum.
Only from topeleven.com, if he notice the forum spot.

But as you are in the clash of clans, what extra has that forum (or the other one) ?

* you know that in Suggestions section, there is a thread about how to improve forum
** why is it urgent ? lol