Until not so long ago, central banks were rather secretive institutions: policy decisions were communicated in a very reserved way, to say the least. For example, the US Federal Reserve used to be silent even about interest rate decisions, leaving the outside world to use market reactions to discern those decisions.
This is a necessary step to solve the too-big-to-fail-problem. Large banks must be able to fail without endangering the stability of the whole system. Otherwise, the government would have to step in to prevent a systemic crisis. This would create an asymmetry: Heads, banks win, tails, taxpayers lose.