The secret ballot is crucial to our republic, and vote-by-mail utterly destroys that. We gotta think more than a millimeter deep, here!
It is NO surprise that Oregon started mass vote-by-mail and then immediately turned hard Left. Vote-by-mail is nothing but a Lefty stalking horse. And any jurisdiction that adopts it will turn hard Left in short order.
Vote-by-mail gets the greedy and unmotivated to vote, makes voter fraud much easier, and destroys the secret ballot. ALL things that the hard Left wants!