Apparently they're no longer to stop global terrorism, but to cut down on identity theft. Funny that, by providing a single, copyable form of identification.
Tony Blair has told MPs that identity theft costs the UK "billions of pounds each year" shortly before new plans for identity cards are unveiled.

Blair defends identity card plan
I can see a new approach from the treasury here as well. Banks compensating victims of identity fraud is simply a cunning tax evasion scheme to reduce their corporation tax liabilities, and should be suitably punished.