The cubit, foot and other units of length can be viewed as a tool to extend the Pharaoh's power throughout Egypt. The sacred foot was an emblem of power as the ideographs below indicate. There is an ideograph similar to that of the tcheser (foot) in which the hand is holding what appears to be a scepter. The royal cubit may therefore be a symbol of excellence.
One of the duties of the scribes was to distribute goods. When precision was required the royal measures were beyond question.