The issue with ID cards is the surrounding rules.
We all have to prove who we are in many ways, whether to law enforcement, banks, the courts, social security, for passport and other travel permits, parentage etc etc. But that’s a process that’s in our hands.
The difficulty with ID cards is that they’re useless for their stated purpose unless it’s an offence not to carry one, so it has to be produced on request. At the moment you can be required to attend a police station within x days with a driving licence or whatever. An ID card could see you arrested on the spot if it’s not with you.