The Fed is probably concerned that, if the idea catches on, trillions in deposits could be vacuumed out of the fractional reserve banking system, leaving less a

The Fed is probably concerned that, if the idea catches on, trillions in deposits could be vacuumed out of the fractional reserve banking system, leaving less available for lending. If that were to happen, the Fed would lose considerable influence over liquidity. Its only lever on narrow banks would be to adjust the deposit rate encouraging savers to go elsewhere.