The Archbishop of Canterbury recently lamented the loss of Christian culture (here) and laid the blame at the feet of 'pluralistic' education.
I have some sympathy with this. In promoting everything, we promote nothing. At a local school recently year 6 and 7 children were told to look at SE Asia and pick a dominant religion to investigate. They were specifically told not to look at Christianity. The teacher wasn't being (she thought) anti-Christian she was rather making the assumption that most kids in that school would know about Christianity. I think this assumption makes more assumptions than it asserts.
I well remember when I was a teacher in the 70s, our principal challenging the school over the Easter weekend to find out what Easter was all about.
In those days most of the kids had some idea it was about Jesus and his crucifixion. Not so sure that is true. I certainly can no longer assume 30 years aftyer I was ordained that a random group of Aussies can more or less sustain the Lord's Prayer with a little help from their friends. This is not, I think, because of an embarrassment about praying publicly. It is because by and large we have no clue.
Strangely the army did quite a lot to sustain religious culture. So, service men and women of WWII and to a lesser extent Vietnam, probably were made to recite the Lord's Prayer on parade. Now that there are less of them they don't permeate a funeral in the same way so you can't always be assured even the 'traditional' words will be picked up.
Does it matter? The loss of common heritage. I think it does. I always go back to the way the Bible stories permeate English literature.
How on earth do you (for example) understand Wilfred Owen's devastating poem. The Parable of the Young Man and the Old...if you don't understand what the sacrifice of Isaac is all about, or that it comes from the bible, or what sacrifice is about?
I think Rowan Williams is right, not just or only from the religious point of view. But from the cultural point fo view also.