At this point it would even be easy to lore-ify their removal(and SE lurves it some lore). Originally, unlocking a job was all about the player rediscovering ancient, forgotten arts related to their (relatively)mundane class or becoming privy to ones held only by a select few in the current era. At this point though you've got thousands of players who've figured all this stuff out. Going into 3.X, they could have all the guilds switch directly to the job, with NPCs there remarking how they used to teach a much more basic discipline but thanks to the efforts of adventurers, techniques lost to the sands of time are now recovered for all.