http://www.usgamer.net/articles/fina...lood-expansion

Yoshida:
One example of this was the Summoner. That was highly demanded, but once it was in, there were more and more requests. "You should be able to summon all the Summons and Eidolons!" That can push a person to think, "Oh, I shouldn't have included a Summoner in there." It is something that we need to be very mindful of, because something that could be implemented into an MMO may not necessarily be fun in a standalone Final Fantasy. The opposite is also true; an FF element that people have a strong attachment to may not translate well into the world of an MMO.
I mean, how hard is it to add some pets? WoW hunters has several. My elementalist in GW2 can summon more stuff than my FFXIV summoner. My warlock in WoW has more pets than my FFXIV summoner. Why is this allowed?

It wouldn't be acceptable for black mages to never get any more new spells, would it?

You neglect the job so much and then get surprised that people say that it shouldn't have been added at all. You know what? People would say the same thing about black mages if all they could use was Fire I, Blizzard I and Thunder I. No Flare, no Fire III, no anything else.