Estonia went electric everything for... Well. Almost everything.

https://en.m.wikipedia.org/wiki/Digital_signature_in_Estonia

https://e-estonia.com/solutions/e-identity/

Some countries implement verified authentication schemes for their inhabitants that can be linked to both government and private services.

I.e. you have one login to use when filing taxes, getting health data, social security, interacting with your local school etc.

It has to do with widespread deployment and a central trust authority - that the specific citizen holding the specific citizen's cert. Service providers don't have to deal with the massive pain that is identity verification, there's no cumbersome stuff like faxing someone a gas bill to prove their identity.