My guess is with mostly all MMOs offering some sort of spec option per class, SE didn't want to fall out of the loop. Point allocation would scare away casual players since it seems complicated. Due to Final Fantasy not being limited to a set number of jobs, they can create a ton of them and offer them as specs to classes. I personally love the idea. I'm playing as an Arcanist...need more DPS? I'll switch over to Summoner. Need me to help heal instead? Damn, I haven't leveled Conjurer, but I can switch over to Scholar since I have Arcanist at level 50!

Classes can be used for leveling and for adding new weapon types. Hopefully we'll get one or two classes a year at the very least.