It's that players don't play. I've modded more than one and it all starts off great and then life goes on or players don't get the lines they want and they stop playing and it just... it always happens. I've modded or played in most of the games around - not all, though - and that's how it always seems to happen. It doesn't seem to matter if activity is required or if other things are or aren't allowed, it just... really never seems to take off and I don't know why.