Kuroda has been very effective in surprising the financial markets today: why? (we have been lucky not play the game this time).
Real economy might have liked a move, financial actors might have felt the additional pain in advance.
Within the very close future we will have more material reasons to see action, hopefully we will not see it. In June we will experince the market reaction to any decision taken by the FED, we will also experience the markets reaction to the UK referendum.
The above reasons might offer at least a partial answer to the why.