> Where I am in IL you don't need to show photo ID to vote, so the level of verification that occurs in person vs by mail is the same.

It's not quite the same. If you go in person, you fill out a piece of paper and sign it. You turn in that paper to get your ballot, and they compare the signature. But, if the poll worker says that your signature doesn't match, you have the opportunity to verify yourself with ID, etc. And there is supposed to be Democrat and Republican election judges present to agree and consent to giving you a ballot.

If you vote by mail and there is an issue, you have no opportunity to resolve any problems.