Yeah, forget applying any sort of reality to 4e shields, there is none. No shield in the history of man ever worked the way the light shield in 4e does. In ALL cases you grip a hand grip. Later medieval shields and some earlier large sized shields like the Roman ones also had some type of strap, usually over the shoulder but later a loop the forearm passed through. I know of no shield design which ever left a hand free, nor would such a thing be at all workable.
However, the rules are what they are and changing it would really seriously mess with the whole set of trade offs built around how it works. For the most part shields aren't much use really. Almost any character that uses one could pick better options. None of the shield enchantments are even worth thinking about either. That however may largely be the fault of IAoP.