"I am the wisest man alive, for I know one thing, and that is that I know nothing." ~Socrates

Are you aware that the US is not the only country implementing the Real ID? The UK is also implementing a biometric ID, also on the "voluntary" basis. If brits do not volunteer to get the ID, they (like current US rules) can not travel, can not get government assistance (SS, grants, etc.) and can not open a bank account.
Another requirement is that they can not buy gas, and - like the US Homeland Security Department - the UK government has the power to add more requirements.