In 5,000 years of recorded history, there isn’t another known instance of negative interest rates. Now we’ve got about $13 trillion of securities with negative interest rates around the world. So far, that hasn’t happened in the United States, but don’t assume it won’t when we finally get a recession.
Money is a commodity. It has a price just like oil, gold, wheat or any other commodity. When the market isn’t allowed to set the price, bad things happen- misallocation of capital basically. You know this if you’ve tried to save money and found that the only way to get a return above inflation is to make investments you’d really prefer not to make (How many of you remember 6% CDs?).