A central bank that focuses intently on asset prices looks as if it is trying to control too many elements of the economy. Part of the recent successes of central banks throughout the world has been that they have narrowed their focus and have more actively communicated what they can and cannot do.
Specifically, central banks have argued that they are less capable of controlling real economic trends in the long run and should therefore focus more on price stability and damping short-term economic fluctuations. By narrowing their focus, central banks in recent years have been able to increase public support for their independence.