Take for example a region where the economy is overheating, like western Canada with its oil sands development. The economy there is holding up quite well. However, that might lead to some problems, such as an increase in the value of the Canadian dollar. That could hinder other regions, like Quebec in particular, which is very dependent on its exports to the U.S.
Therefore, setting the interest rate according to the overall state of the economy at a given time can place some regions at a disadvantage. Do you not take that into account?