That's because the FFXIV forum software is VBulletin, (along with the FFXI forum), which is third-party forum software, and a really old one at that, so SE are limited by the limitations of the software (having been a moderator on an old forum that also used VBulletin years ago, I can vouch how long in the tooth it really is).

Unfortunately, I doubt SE are really interested in spending the money upgrading to newer software or taking the time to actually design their own forum, as forums are kind of outdated compared to modern social media systems.