The difference is there's no hard dependency on centralized authority or any kind of complex web or mobile technologies.
IT is complicated. Many orgs are still running ridiculous old systems. A lot of people don't have mobiles phones, or generally don't know how to use them properly, may not have data services or even an email address. The 'COVID tracer' app issued by gov. Canada has barely anyone using it.
TN visas (NAFTA visas for US/Can/Mexico) are obtained at the border, it's just something stapled into your passport. That's it. And that entitles you to live in a foreign country. We could feasibly do the same with COVID tags.
It's really hard to set up government agencies that operate effectively with all the bells and whistles, it's costly, tons of consultants, tons of service calls & support ... by leveraging the DMV or it's equivalent, you already have most of the infrastructure in place: they know how to check and issue IDs, they have processes for appointments, service calls, queuing, putting out support content that meets standards (i.e. disabled, elderly), actual phone numbers and physical people to speak to for those who are used to that. For the same reason bank tellers still exist.
We used to do some amazingly complicated things without IT.