Hence the nostalgia factor. Zidane's the thief, Vivi's the powerful Black Mage, Dagger's the White Mage (with a bit of summoner thrown in a la Rydia but the other way around), Steiner's the Fighter, Freya's the Dragoon, Quina's the Blue Mage, Eiko's the Summoner (still w/ white magic, guess the Rydia style summoner stuck) and Amarant's the Monk. All classic classes. Sure, you could categorize the characters of FF7 and FF8 like that, but they could be anything. In FF9, the characters stuck with their classes and the respective abilities.