User blog comment:Rupert Giles/Introducing Updated Global Navigation/@comment-5448890-20141030143225/@comment-452-20141030194348

Chat does not contain any ads, therefore there is no incentive to enable it by default. It also would create more work for admins to police.

Achievements do not directly increase ad-views, and may decrease them slightly if more users register, as registered users see fewer ads. It could be argued that achievements == more edits == more content == more visitors == more ad-views, but I do not know whether this is factual. Several editors have told me that they would edit less if I enabled achievements. (It also would create more work for admins to police achievement-spammers)

Does the new Maps feature display ads? I haven't investigated it.

Anyway, Wikia has always been a for-profit company. Someone is obviously encouraging the organisation to increase ad revenue - that's what for-profit companies generally do.

Wikia introducing another feature to increase ad-views is not the end of Wikia as you've known it, it is standard practice.