Competes and avoids politics.
Federal Reserve ND, Board of Governors of the Federal Reserve System, "What is the difference between monetary policy and fiscal policy, and how are they related?", https://www.federalreserve.gov/faqs/money_12855.htm
Monetary policy refers to the actions of central banks to achieve macroeconomic policy objectives such as price stability, full employment, and stable economic growth. Fiscal policy refers to the tax and spending policies of the federal government. Fiscal policy decisions are determined by the Congress and the Administration; the Fed plays no role in determining fiscal policy.
The U.S. Congress established maximum employment and price stability as the macroeconomic objectives for the Federal Reserve; they are sometimes referred to as the Federal Reserve's dual mandate. Apart from these overarching objectives, the Congress determined that operational conduct of monetary policy should be free from political influence. As a result, the Federal Reserve is an independent agency of the federal government.