Unless someone is literally putting their money under the mattress, the money is in a bank which is loaning most of it out, so the money is almost never actually "hoarded".
Banks are just sitting on their cash. Also, the Fed is paying the banks not to loan out this money, currently 0.5%.
Forces business investment (or dividends), but promotes savings for individuals.
On a multinational scale penalizing Apple and Ford cash reserves, but not extending the same penalties to Samsung, Xiaomi or Toyota, gives the foreign players greater flexibility.