In FF11 you could unlock any advanced job at lvl 30. At least at the time I played. I think in FF14 they could easily make all the advanced jobs start at lvl 30 in some of the old zones, and then just make you wait till you are at the lvl 50 or 60 mark to start your job quests if they don't want to make job quests from lvl 30 up to lvl 50/60.