You could argue that hiding both the HP and MP bars together wouldn't have much impact on your play. As long as you've got a healer watching your HP, do you really need to see it? Doesn't apply to solo so well, but, eh..

It could be in the future they'll continue moving resources to job-specific features, but, "MP" is a pretty generic standard thing for an rpg. There may or may not be examples throughout the genre of characters that don't use MP at all still stuck with the resource because every character has it.

Shoulda just made it so physicals get the TP bar, and magicals get the MP. But I suppose things like PLD really throw a wrench into that idea.