Identity Crises

It is beyond my comprehension why British politicians waste so much time talking about implementing an identity card scheme for the UK when, surely, it would make a great deal more sense to simply make it a legal requirement for all Britons to hold a passport.

The technology and infrastructure for the production of passports is already in place. Citizens could simply be compelled to acquire a passport upon reaching the age of 18 if they did not already have one; young offenders could be issued a passport as part of their processing and so on.

In order to spare people from having to carry the passport at all times, it could be agreed that a plasticated photocopy of the page containing the photograph and other personal details of the holder would be sufficient for the purposes of being identified in the street, provided that the individual were able to produce the passport itself on demand i.e. could go with police to their home to fetch it or produce it at a police station within a given period.

This is already done in several countries and seems to work perfectly well. Citizens would then have a passport ready if they wished or needed to travel at any time as well as being able to identify themselves. It seems obvious to me, but perhaps I'm missing something? What, I wonder, could that be?