I think a big reason the BBs are hesitant to go on a huge advertising campaign is because they've already tried that. Several years ago they went on a huge ad blitz and got up to 60k users and then what happened? All those guys left.
If they invested heavily in advertising again, who's to say the same thing doesn't happen? After all, while they've added some features to help new managers, the game has remained more or less the same plus they have no mobile site or app.