It's just something to overlook for the sake of player convenience. In games such as The Legend of Zelda: Breath of the Wild pretty much every NPC reacts to changes in weather, the presence of monsters and the day/night cycle. As a result, it can be easy to miss side quests that would otherwise be readily available if those NPC's were simply standing around in the same spot no matter what was going on around them. I'm content with FFXIV's current approach...and it isn't hard to head-canon the NPC's going about their daily lives when the adventurer isn't standing right by them.