User blog comment:Sannse/Images on this wiki/@comment-24883907-20120329153714/@comment-8-20120401191605

Yes, we've considered that very seriously. Unfortunately, it would actually take more resources than you would think to set up and maintain and so isn't something we can do at the moment.

You are right that each wiki is individual, and we try to allow for that in other ways (not interfering in local decisions unless absolutely necessary for example), but until/unless we are able to have an integrated system for age-gating, we have to manage Wikia as a whole in this area.