I remember a lot of talk about weather the Shield is a weapon or a piece of armor, not only ingame but historically as well.
I guess, in whichever profession they'd put them in, the other one would have valid objections.
They finally chose to include them in Weaponsmithing just because Armorsmithing was already producing more different equipable items (numerically - body armor, helms, gloves, boots, belts, cloaks). Weaponsmithing also provides chance to bonus skill levels on its products, which kind of worked better for the shields.
They're still sold in the Armor Shop in every province, though, which means they're considered "armor" as well.
