> those point to the uselessness of the CPI as a matric
Unless you're setting federal policy, it probably is useless to you. For personal forecasting, you're better off using the CPI calculated for your state or metropolitan area. (If you're procuring at a national scale, you're looking at a producer index.)
CPI plays a huge role in our everyday lives though. From cost of living raises to entitlement programs, it all moves based on inflation numbers and the CPI. The Fed even considers these numbers when watching the economy and deciding on fiscal policy, setting the Fed Funds Rate and impacting interest rates across the board.
Unless you're setting federal policy, it probably is useless to you. For personal forecasting, you're better off using the CPI calculated for your state or metropolitan area. (If you're procuring at a national scale, you're looking at a producer index.)