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.
A central bank that expanded its focus to asset prices could potentially weaken its public support and may even cause the public to worry that it is too powerful and has undue influence over all aspects of the economy. Too much focus on asset prices might also weaken support for a central bank by leading to public confusion about its objectives.