It's a great way to determine the efficiency of your campaign, compare in-game WWII with RL WWII and it's very immersive, i.e. good for flavour. Have you ever wondered why so many people love various special and elite units with unique icons/sounds/sprites/whatever, even if they are not that much more powerful than standard units? Why some people make such a fuss about ship names? I think the reasons are very similar.
and a great way to tweak things