I just feel like adding more NPCs "going about their day" brings more attention to the weird "Time loop" effect of seeing the same thing play out over and over. We already have it to an extent, with things like those two kids at the Ishgardian market that you'll come across at various stages of their shopping trip over and over, same sequence, same dialogue. It makes the world seem more alive the first time you see them; less so when you've seen them do the exact same thing without variation for the tenth time.

In the field zones, FATEs are clearly intended to play this role. People are going about their day and stuff happens to them.