Central Banks will only increase interest rates if the market is good and inflation is picking up. The reverse happens. Economies falter and experience deflation. In this case, authorities typically reduce interest rates in expectation of encouraging people and businesses to invest, this will in turn spur the market. In theory, interest rates can only go to zero, but Japan has performed a fantastic little trick with negative interest rates (That will be an additional chapter if I were to elabourate). During the 2008-09 financial astrophe, the fed cut interest rates from about 3.5% to 0.25%.
The current US interest rate is 1.25-1.5%. We don't have much wriggle room to decrease interest rates if a different downturn were to happen. If government can't cut interest rates satisfactorily, the recession might be protracted. And we all don't want that. With economies so tightly tied. Trouble in 1 country could quickly spread to other countries. Especially with countries such as US.