I can agree that only being told that in order to unlock all the achievements you need to talk to 8 NPCs found somewhere out in the Eorzea is a rather daunting task, at first. It's a big world. Even 8 NPCs spread out across just one zone alone would take a while to locate them all. Something which is being fixed come 1.21 when they'll add the NPC's names and locations to the Achievement UI.

But beyond that, I see no pressing need to reduce the 8 NPCs down to 1. Traveling isn't even a big issue nowadays. Between airships, chocobos, and teleports, moving around the world is a piece of pie.