I'm a moderator on a forum, where a topic named "Offtopic" is right now almost 6300 pages long. Admins just disabled post coutning in a whole offtopic subforum, so no one gets higher postcount from spamming there.
That's nice, but Bethesda likes to keep their forum clean in order to maintain their reputation. You'd be surprised what kind of things can really neck a company these days.
So besides that, there's the moderator-time-argument and the fact that the added value of such a board or topic is naught.
They already closed General Discussion once way back in the days. Community Discussion is one of the things that keep this forum interesting, let's not speed up its demise with useless chat topics.