I totally agree with RAIST.

When developing for cross-platform, developers create code which can be used on each platform (platform-independant code); this saves development time and makes the code easier to maintain. There is code unerlying this platform-independant code, which deals with features unique to the platform(s) it's running on (platform-specific code); this code deals with tasks the platform-independant code wants to do, then the platform-specific code carries out that task based on which platform it's on (e.g. 3D rendering is different on all 3 platforms). It's safe to assume that the platform-independant code and platform-specific code (of all 3 platforms) of FFXI has been coded with the PS2 limitations taken into serious consideration.

So yes, the PS2 may be outdated but removing PS2 support from the game would be a huge task, from a programming perspective, and, in my opinion, it's a task not worth doing.