Why not? For the average citizen prices at the local store are the thing that immediately effects their daily lives and will in turn cause them to change their spending habits accordingly subsequently effecting other parts of the economy beyond basic needs.
Because how much you spend for wheat is not what inflation is (unless the only thing money was used for was to buy wheat). The price changes of any one good is an inaccurate look at inflation. Oil tripled last year but that doesn't mean we went through 300% inflation.
