They use a replicable/swappable sim. In theory anyone could implement their own version that can be put in existing bands.
Like a lot of things. I think this like other options to pay are useful and have their use cases. We don’t need a everyone solution because frankly it doesn’t exist. So I think it’s good to have multiple ways to pay like this.
Barclays needs to buy monzo for their marketing team so they can advertise better perhaps