I guess is that theres no auto attack because
1) Stamina bar, everything you do need a certain amount.
2) Some abilities are reaction base. Example Haymaker. Having Auto attack can ***** it up. Since you basically need to queue the action after you evade
3) I guess ppl forgotten how peeps are complaining that FFXI for some jobs = auto attack wait TP, perform TP, Magic Burst.
Well, SE made a system that needs you to do something, all the time