Yeah, I remember a time when moderators of other boards would close fanfic threads and direct them here. Unfortunately for the traffic of our board, that rule was slowly eroded as more and more new mods got appointed who were unaware of the rule and did not enforce it, making fanfic threads legit across many boards. I raised this point a while ago, and the higher-ups decided to do away with the rule altogether.
We tried to maintain the uniqueness of the fanfic board by allowing direct posting of fics here (whereas the other fanfic threads are only allowed to post links), but that hasn't caught on quite as much as I would have liked to see.
Still, I do think the fanfic board serves other functions than to host a bunch of fandom fic threads unrelated to each other: I've met quite a few other writers on here, whose fandoms I rarely, or never, frequent; but nevertheless we have had some very interesting conversations about writing and fanfic in general. That aspect is what I would really hate to lose if this board is closed, because I don't really see where else these topics can be raised.