Central banks eventually hit a floor where cutting interest rates further stops working

Once a central bank's interest rate nears zero, cutting it further loses its usual power — people would rather hold physical cash than accept a return below zero. Japan hit this 'zero lower bound' in the 1990s, and much of the world followed after 2008, forcing central banks toward unconventional tools like quantitative easing and, in Europe and Japan, cautious experiments with negative rates.

— Wikipedia contributors, Zero lower bound — Encyclopedia entry