Games that are more successful are those that appeal to a wider audience. If FFXIV had solid open-world PvP, it could attract many more players to the game. The current PvP options in this game are limited.
There was once a thread in the PvP forums that suggested a PvP server, which IMO would be a simple solution. It would have absolutely no impact on people who don't want to be involved in open-world PvP. There was the persistent argument that it would 'split the community' (which is selfish if you ask me. PvP players are mostly in frontlines so whats the point?) as well as that square would have to split resources for this pvp server - which isn't something a player has to worry about.