I do appreciate how much it is still used  ---  "stick to the devil you know".   My argument is it is not relevant now. . It is a 19th century solution to market information (price discover).  The arbitrage you describe is not efficient and represents zero sum movements.    The only "winner" is the one facilitating transactions. 

It will not happen overnight, but CME is no longer a necessary means of clearing a market in time or space.   No one know more about the market than the ones making or using the product.  Anyone in between is not adding utility aside from convenience.  Decoupling is an old argument (and occasionally is witnessed) - but the more modern relevant drivers are the amount of local disappearance and the amount of local knowledge that is generated about production and use is easily captured at local markets - without aid from any central price indicator.   Old habits die hard.