I never understood why this helmet is the signature piece in the game. The helmet is weak and I think iron armor overall is weak no matter how much you upgrade it. Why not feature the daedric helmet or a dragonplate helmet as the signature piece for the game? You would think being the dragonborn, that the dragonplate helmet would be the feature piece of skyrim. Here's what I found from the wiki:

-The Iron Helmet is worn by the http://elderscrolls.wikia.com/wiki/Dragonborn in all pre-release trailers and artwork for the game, making it somewhat of a signature piece of armor for the main character.

-The Iron Helmet is a hat available in a game called Team Fortress 2, but with a different name: The Dragonborn Helmet. It can only be worn by the Heavy class and was given away in Genuine quality to people who pre-purchased "The Elder Scrolls V: Skyrim" through Steam.

-The horns on the sides of the helmet change through gender choice. As a male the horns will look as that of the photo provided above. This changes if you make your character a female, the horns will turn more upwards and much more curved than its male counterpart.

I suppose it is becuase the promo pics are of the Dragonborn at the very beginning of his adventures, so no fancy stuff. What I find odd is that he is wearing it along with Light Armor.

Oh well, it's cool looking.

Yeah but iron is the bottom tier material! You would think that if you see the picture on the game or anywhere else that there would be an incentive to get that fancy armor such as the dragonplate armor. Wouldn't that be a major incentive for you and make you want to purchase the game more than the basic iron helmet?

Ancient Nord would have been a better choice,IMO. It would still be a bottom tier armor, though.

I think you're over thinking it here. The helmet was probably a simple aesthetic choice with the intention of being instantly recognisable to everyone and to put across the Nord/Viking look.

Or maybe Todd just liked the iron helmet.

I think it looks very good. Okay its not the best armour but I think it embodies Skyrim the best. Its crude, barbaric, rugged and harsh.

I think it might be so that the player can have the image seen in the advert from early on, if they want it. In the trailers, the Dragonborn wears studded armour with iron gauntlets, boots and helmet... all of which are available within 10-20 minutes of completing Unbound, depending on where you go. So, the player can look like the character in the trailers more or less from the beginning of the game.

EDIT: And it looks cool.