Based on what we see in-game it seems like they're a lot rarer than what player character couples may imply. There's also a lot of historical conflict between the city states and the playable races. If not for the Garlean Empire and Primals requiring a united Eorzea I have no doubt that that would only be a matter of time before infighting occurred.
One major obstacle is that even with it being established that interracial couples are frowned upon a lot of role-players drag real world morality into the mix and so any character who paints it as a negative is usually perceived as a villain or worse yet, it devolves into OOC drama and mudslinging.
One major obstacle is that even with it being established that interracial couples are frowned upon a lot of role-players drag real world morality into the mix and so any character who paints it as a negative is usually perceived as a villain or worse yet, it devolves into OOC drama and mudslinging.