User blog comment:Brandon Rhea/Wiki domains will be changing from wikia.com to fandom.com in early 2019/@comment-4738647-20180816235130

You have to treat each franchise differently. Some have established forums, subreddits, facebook groups, discord chats etc. some have fan-made encyclopedias outside of Wikia because no one bothered to make one here. (The following is subjective) perhaps despite non-Wikia encyclopedias existing, editors created/started editing on a Wiki on Wikia/FANDOM because they disagreed over the non-Wikia Website's writing style or quality of referencing (and, even if you don't want to hear it, vice-versa).

You can't force the fanbase of every franchise to have their center for social media and discussions on Wikia/FANDOM. We came here to create encyclopedias, if a franchise wasn't big enough to have dedicated online discussion threads or news/bloposts, it is nice to have the option to have one on Wikia/FANDOM, but franchises that already do that have got their territory covered and don't need FANDOM to intrude on it.

Furthemore,  a Wikia here may already have agreements with off-Wikia communities on what roles the websites play in the fanbase.