I was at a wedding this Saturday. During the service, the Our Father was said. It was rather disconcerting to notice that looking round the church barely anyone under 40 was joining in with it. If I was charitable I'd say it was because they were shy, but I think it was more likely to be that they simply didn't know it; something I found highly depressing. Knowledge of basic prayers and the broad shape of the liturgy and the liturgical year ought to be a fairly fundamental part of people's general knowledge.
This kind of knowledge is not something that should only belong to practicing Christians. For anyone with an interest in history, literature or popular culture, a basic understanding of the tenets of Christianity is essential. People need not believe in it, but they should at least grasp the basics as part of their basic general knowledge. How can people understand huge chunks of British, European and World history, art and literature without appreciating a key aspect of the social context in which it was created? This applies to everything from Shakespeare, Chaucer and James Joyce through Da Vinci, Millais, Chagall and Stanley Spencer to Father Ted and the video of 'Like a Prayer' by Madonna.
When teaching medieval archaeology I can no longer assume even a basic knowledge of Christianity, and have to provide crib sheets to basic concepts such as the Eucharist and the Passion. This is not a call for increased belief in (I'm a lapsed Catholic- though not so lapsed I don't feel guilty about it), but a knowledge of a key strand of the European cultural inheritance.