Our head of state is supposed to be completely apolitical. If he started commenting on the situation with anything more than the usual platitudes he'd get into serious trouble.
But that is a bit of a movable feast isn't it. We often get platitudes when they are perhaps not needed, but words from the head of state when there is a threat to the social cohesion of the ... err ... state then words, even rather bland platitudes, are surely appropriate rather than silence.
I do not blame him for his silence. In this country, it is the job of the prime minister to do the leading and the pulling together and so on.
Now I know this is a UK issue, but (as with my example on 9/11) there are times when the head of state needs to lead the state - in times of great trauma to other countries for example. Their heads of state (even ceremonial ones) tend to do this for us, yet ours too often seems to consider themselves above this. I think that comes across as rather arrogant I'm afraid.
The role of the PM is different and where there are other countries where their is a political PM-style leader and a ceremonial head of state their heads of state still seem to do stuff that ours won't.