The only voting machines that make any sense are those that can take human readable ballots and count them. And even then that needs to be coupled with audits and other basic means to verify that they function as intended and required by law.

(Optical scan, basically)

The basic problem with voting machines casting actual votes is that they do not make a record of voter intent. They make a record of what they think the voter intent was. The actual record of voter intent walks out the building, or is a grease smudge on a screen somewhere. Lost.

They are all votes by proxy.

Because we make votes anonymous, the chain of trust between the voter, their intent, and the record of that intent, is super important. That record needs to be used directly, or we've got issues with how trustworthy the process is. That record is needed should there be issues too.

Electronic machines do not record voter intent, and that is the primary thing of value in an election.

When a voter makes some mark on a physical ballot with a pencil, pen or some other device, they can verify that record is accurate, in line with their intent, and that means that they have confidence that their vote was correctly cast. The vital chain of trust between voter intent and the record of said intent is intact.

Follow that up by using that record directly, (optical scan or simple, human count) and we've got a process, that if necessary can be hauled into a court of law, or manually evaluated by humans, to ensure that we understand the outcome of the election.

Paperless machines are so untrustworthy that nobody can even know who won an election! No potential for review, oversight exists! (Looking at you South Carolina)

When we provide input to a touchscreen, or via button press, or any other simple means, the intent is expressed at that time mechanically, but the electronic record isn't the same as a physical mark.

The truth is, the voter cannot see the vote record directly, because it is electronic. It is just a temporary state. Enabling technology is required for the voter to see the record. In this sense, the record of their vote is isolated from them, and they are forced to trust the input and output of the machine, again a vote by proxy.

This is fundamentally untrustworthy.

An example I have given to kind of simulate this involves a person in a secure room alone. You the voter walk up to a window, and you tell them what your vote is. They go make a record somewhere that you cannot see, and then they verbally confirm your vote, or maybe hold up a card or something. The key thing to understand is the voter has to trust that person, they don't see the little invisible record off to the side, nobody does.

Essentially, there's no chain of trust between the voter and the record of their vote. And no reasonable person would trust such an arrangement to be an accurate election, a trustworthy one. That is basically what voting machines do. They get between voters and the enduring record of their voter intent.

I struggle to communicate this in ways that ordinary people can understand. It's really a problem. People see computers and all the magical things that they do, and they want to trust them. And in a lot of places means and methods they can trust them. Voting is different because it's anonymous, and we don't link people to votes, which means those intent records really matter.