If a money supply remains constant while the economy grows, eventually the money supply becomes inadequate to facilitate trade throughout the entire economy. Consequences vary, but all are disruptive.
This is a fallacy! How money supply becomes inadequate? Money is a measure not fuel for economic growth. By increasing money supply as economy grows you are in fact rewarding a group of participating parties with extra money they do not deserve. You are creating bubbles! Bubbles are much more disruptive than slower growth.