I feel like the main reason for that is that all the zones are supposed to be high-populated thanks to players hanging out there. Which happens mostly in the beginning of expansion and during the major patches, and at the rest time people are just somewhere doind their own tasks.
I felt the same about The Azime Steppes during Stormblood - when you look at Xaela's lore, you expect the area being highly inhabited with all the nomad tribes (51 of them, and those are just known, quite sure there can be more) and little camps, but in reality it's a just a nearly empty steppe, and main source of meeting Auri in fields is lore based FATEs.
That said, with how almost every area was designed to be, what this game probably needs, is a big RP community that hangs out not just in Limsa/Ul'Dah, but in actual world outside of these cities. Or more random NPCs wandering around to make places more lively than they are right now.