> So do ZKP based voting systems.

Assuming no vulnerabilities on the ZKP system, a perfect implementation and no information leak from other sources.

> What do you mean by this?

I assume that ensuring that the person voting is who they claim they are. If someone steals the certificates of that person, they could impersonate them.

> This is a lot of friction which prevents many people from voting.

In Spain (and I guess in a lot of other countries) voting in-person means walking to the closest polling center (99% of the time it's less than 10 minute walk) on a Sunday, picking up the paper, doing the queue (maybe another 10 minutes) and walking out. The alternative is mail-in voting, which usually takes a few minutes of walking to the closest post-office, signing some documents and waiting for the ballot to come. Compare that with getting the certificates, storing them securely, downloading the program to do the voting, installing it, praying it works, then using the program and cast the vote. Think of all the people who aren't good with computers, and how easy would it be for them to do all those steps correctly.

In the ideal case I agree that electronic voting systems would be better. But the world is not ideal, quite a lot of things can go wrong with them because of their complexity and detecting those issues will be difficult. On the other hand, paper voting is fairly simple, the number of things that can go wrong is low and easy to detect by anyone.

Government-issued certificates for electronic voting are a terrible solution because it is trivial to generate millions of certificates for fictious voters and vote in their name.

Friction to prevent people from voting is a US phenomenon where voting participation (i.e. turning up and declaring something, even if it is an abstention) is not considered a legal obligation - and thus, the lack of participation is not viewed as a possible attempt to interfere with democracy.