No, that is not the only thing these apps display. From the article:
>depending on the state, it can include details like their name, address, phone number and party affiliation and when they voted.
Emphasis mine. And if you don't think party affiliation is a big deal, then you haven't been listening to the rhetoric used to describe the parties lately.
One method is to simply not allow people to copy it. I can go to the department and request the information, but I can't leave the building with any digital or physical copy (photoing inside is forbidden). Technically within the legal definition of public information. The other method is using copyright to grant permission for private use but not distribution, which mean no one has permission to put the public information online. That way its publicly available to request from the department but it will not be published online. The third method is not really a method but simply relying on the gdpr. The information may be public but there are still legal limits on the kind of databases people may have about private information.
I've known this information about my friends and neighbors for the better part of the last decade. In most states this is public info and you can even look it up from a web form using name, zip, and dob.
But now it's in an app so the world is ending.