I carry my driving licence too, but by choice.

Lisa Nandy was just on Sky news and explicitly said that it is optional to carry it. You'd apparently "have an ID" but you don't have to carry it.

I'm not sure what that means for why they need it. Apparently to check work eligibility easily instead of one of several means that are, in her words, "more easily forged".

You could quite easily develop a system like the driving licence check (for when you rent a car, for example, to check your driving status and points) to provide extra information anonymously like age range or work status or whatever you wanted. In fact if we were still in the EU we'd be able to participate in the beta that Spain is spearheading for age verification: https://ageverification.dev/. It's goals are explicitly privacy focused so I'd encourage people to read the details.

As a technology challenge I don't think there's a good argument not to have such a system rather than the patch work one we have now that was designed and built close to hundreds of years ago. However politically selling something like this to British people is always going to be the hard part.