That's probably because of the nature of the game as a whole. Unlike most games, the forums are an integral of TB itself. I don't think I can recall any games that have almost as many active players on the forums than they do the actual game. (If you know of one, lmk cause I'm way too young to be assuming such things)

It's odd because it seems like this currency system would be an obvious thing to implement, but most if not all games don't have it.

TB was just ahead of its time in regards to all the functions it brought for something made in 2006.