Maybe it's PR to encourage take up, I have 2 colleagues who want it if they can have an holiday.
For the moment, I am certain that's true: get the idea in people's minds, get people talking about it, get the idea of "vaccine passports" part of the new normal (vomits at the phrase). The government's strategy of testing the public's reaction by press leaking is now legendary.
It's going to face a lot of practical problems, though, and will be nowhere near as simple as the government are making it out to be: it will probably take a long time to get this idea working.
Do I approve of this idea? I'm on the fence. While I am generally dead against any erosion of our civil liberties, any attempt by the government to micromanage our lives, I suppose it's not so different from needing to have a passport in general, to be able to travel abroad.