Method of social control. The governemtn creates a database of all your biometric information, and denies you access to essential services if you cannot present it on demand.
You'll have to pay for it, and if you lose it, you'll be fined.
You: I've been in a car accident, I've lost a lot blood, please help me!
Them: Where's your ID card son?
You: It was burned in the crash, like half my body.
Them: Fuck you mate, welcome to 21st Britain.