Possibilities get realised such as regular remote checks (ie selfie to prove you are the id owner holder, address proof, etc, flagging odd id holder behaviour or employer, etc). Currently, you cannot do this, no visibility into who works where and where that person even resembles the person meant to be working for [insert gig company].
The government absolutely knows where I work, are you joking? That's what NI numbers are for. You seriously think there isn't a join table in a government database with my NI number and passport number?
When the driver signs up, check their passport or driving license in the normal manner, and take a matching portrait you keep on file. Any time you want to, compare a selfie to the portrait on file.
Reason they don't do this is it's profitable to hire people who can't legally work in the UK, if they can get away with it - and the government lets them get away with it.
Who exactly are we solving for?
Simple. Overstaying or/and expired passport will lead to that. Valid status is not a fixed binary state. It is better described as a function of personal id, rights docs and current time. Currently, the checks are more akin to updating a Boolean column on rare occasions. Digital id countries do checks more like function calls that you can perform easily and quickly