The idea is that some npcs won't move from their station due to noise, or wont leave a certain area (like aegis soldiers on the beach during combat). This way the player cant get an entire group of guards to abandon their post so they can sneak past or loot, and cant lure say a sniper into a crappy vulnerable position when they'd be better off way back. I think mainly it'd be best for snipers, xbows, and other long-range high detection types.
