There are a few that could potentially branch into different jobs, only a few at most, and when they could just make brand new jobs not beholden to base classes it just feels unnecessary to me.

I doubt they'll ever remove the classes that are there though. Not only do they have their own guilds and stories that would be awkward to remove, but many of the JOB questlines bring back npcs from the class quests. The paladin SB and SHB quests, the monk SB quests, some of the Ninja quests etc.