There is still tons of ceremony for mail in ballots, it just happens asynchronously to the voter making selections. That's true of paper ballots as well, as significant parts of the ceremony happens after the poll closes during the count.
The biggest problem is that email and online voting suffer from a lack of anonymity.
In person: voter eligibility is confirmed and marked executed, voter makes selections, ballot securely placed in box without being read.
Mail: voter eligibility is confirmed, ballot sent, voter makes selections, voter mails ballot back secured against tampering, voter eligibility is re-confirmed and marked executed, ballot securely placed in box without ever being read.
In both cases all the poll worker steps are overseen by election scrutineers who can confirm all legal requirements were adhered to, in particular that no one knows who anyone voted for, just that the vote was collected.
Email cannot replicate the separation of the voter eligibility verification with the ballot counting. No matter what you do there will always be pathways to link a specific voter to the ballot they cast.
> Email cannot replicate the separation of the voter eligibility verification with the ballot counting
Yes it can, that's what I was on about with the whole "sealed" ballot thing but didn't feel like harping with the details. Once you fill out your ballot you encrypt it with your state election official's election specific public key and the attach it to the email—the digital "put it in the inner envelope." Poll worker confirms eligibility and puts just the encrypted ballot in the drop box. At this point in the process they couldn't look at the vote even if they wanted to. Then when it's time for counting they decrypt each one and count it.
Again is it practical or accessible to your grandma? No but it's exactly the same as mail in voting.
There is absolutely no way to guarantee the process of detaching the outer ballot from the inner one doesn't retain a link to the voter. There are problems on 2 levels: the math proofs behind cryptography involved (which is being worked on, but not currently solved) and the building a verifiable implementation that honours all the requirements in a provable way. That's currently easier, but fails hard on the public trust front due to the overwhelming complexity.
Moving mail ballots to email is not currently possible or even very viable.
Well yeah the poll worker could just write the voter's name on the inner envelope but that isn't a deal breaker. There's no need for math proofs or whatever nonsense. The cryptography is just to provide a light barrier to the poll worker who's being observed detaching the two things just the same as mail in ballots like the glue on the inner envelope. It doesn't need to be verifiable or perfectly secure because again mail in ballots aren't. Someone could steam the glue off, look at the ballot, and reseal it (or replace it entirely) but that doesn't happen because they're being observed.
The point of this exercise isn't to say we actually do email in voting but to demonstrate that you can absolutely build a system that's exactly as understandable and trustworthy as the mail in ballot system but digital because it is the mail in ballot system just s/USPS/a series of tubes.
I get wanting to be wary of bespoke voting software but in this hypothetical it's a human watching the screen of a boring Windows workstation provided by the state's IT department as the poll worker uses Microsoft Outlook and puts ballots in a folder. At what point is the threat vector remote enough with these devices we're fine trusting literally everything else in our lives to that it's paranoia rather than a legitimate threat? I mean even if you are that paranoid let anyone who cares analyze the machine afterward I guess. And in this system recounts are trivial, you still have all the original data.
The biggest problem is that email and online voting suffer from a lack of anonymity.
In person: voter eligibility is confirmed and marked executed, voter makes selections, ballot securely placed in box without being read.
Mail: voter eligibility is confirmed, ballot sent, voter makes selections, voter mails ballot back secured against tampering, voter eligibility is re-confirmed and marked executed, ballot securely placed in box without ever being read.
In both cases all the poll worker steps are overseen by election scrutineers who can confirm all legal requirements were adhered to, in particular that no one knows who anyone voted for, just that the vote was collected.
Email cannot replicate the separation of the voter eligibility verification with the ballot counting. No matter what you do there will always be pathways to link a specific voter to the ballot they cast.