I haven't read every single post in this 22 page thread. But SE have already said that the new jobs won't start at level 1, there's the first reason to not have them available to new players starting out. They are also jobs that - in the story - are local to Ishgard and if you can't get to Ishgard until you've completed the story (spoiler free here but you know why you can't) then how do you intend for these people who are yet to complete the story to get their job quests (if said jobs were made available)?

I have no problem with blocking these jobs behind the story content, especially since they are local to Ishgard in this world. I think there will be more reasons to have them story locked when we get further information about them (cross class skills?) but there's no point going into them as that would just be speculation.