Sorry, but explain to me how I'm able to submit my taxes securely every year online, or pay for my marketplace insurance securely every month, but voting on our own digital devices is somehow beyond reach of what we can technically fathom?
Someone might have an interest in impersonating you to steal your tax refund -- these scams do happen.
Impersonating a bunch of voters is potentially easier when you're just presenting yourself as a computer with an internet connection rather than a flesh-and-blood human body.
Because the threat models are completely different.
For starters, if you get your taxes wrong, or if someone fraudulently tries to file on your behalf, it's a reversible process. You can fix it after-the-fact.
Ballots have to be anonymous (secret ballot) and also non-verifiable (to prevent vote-selling). There's no redoing an election later on, or asking a person to confirm their previous vote.
Bottom line is that we have a literal army of software engineers in this country that are capable of figuring this stuff out if it was a priority to get voting to 100% turnout. We split the atom and landed on the moon, I'm pretty confident we can figure out mobile voting.
Next time you try to use it, consider how much credibility you'd give to this argument: "We had men land on the moon and return safely, so we can surely land men on the sun and return them safely".
A single fraudulent vote doesn’t benefit anyone, but thousands of them benefit someone greatly, and it’s difficult to trace, as it looks the same as a regular vote.