Considering TES is a Single-player game series, cosmetic is actually just as important as usefulness: You don't have any other player that you need to beat, thus requiring better armor - you just have a bunch of NPCs to beat.
Having the option to have a pauldron on one shoulder, and not on the other, or a small on one and a bigger one on the other, is very cool, as it adds realism and immersion.
Realism: In the Medieval times, when buying armor, people bought piece by piece - they didn't buy a full set of boots, gloves, trousers and shirt (Fallout).
And about Pauldrons - if one of your pauldron is destroyed, do you take off the other one, and buy a full new set? No, you keep the one intact, and buy/find a new one... The same goes for everything else. (Yes, by today's standards we buy a new set of shoes when one is ruined, but we live in a time where we spend much more money than we should, whereas in the medieval times, they didn't have that much money)
Immersion: Being able to fully customize your armor makes the game so much more enjoyable, and you can have so many different combinations of armor!
Well, that is my rant for today, and I also agree with the OP of course, having more types of protection and such is a good idea.