It doesn't have to be: With a glut of global savings that started even before the 2008-09 financial crisis, central bankers slashed interest rates to almost nothing and finally to zero. They also "printed" electronic money to buy trillions of dollars in bonds to push down the longer-term rates that they can't control directly. When even that left their economies close to stall speed, some central banks in Europe, soon followed by Japan, took things into uncharted territory. They weren't exactly sure it would work, but rates have successfully gone as low as negative 0.75% in Switzerland without huge problems. If bonds and bank deposits that didn't earn anything weren't enough to get money flowing out of people's pockets, then charging people and companies for saving seemed like the logical next step