For the vast majority of people, FFXIV and WoW are really different experiences. FFXIV doesn't take what it happens to attract the majority of the WoW base be default. It essentially has no PVP, the artstyle is off putting for people that aren't into anime or Japanese games.

If you ever read the community chat in general, forums, dungeons etc, you will see there is little fanbase overlap.

Truth is most people would rather quit MMOs than try another one, for many WoW is their first and last MMO. Investment in this genre means a lot.