That has not been happening for all that long. The mail was deemed to be quite good enough through most of my life.
Yes, quite true but I was answering the OP's question. And also, it should be remembered that all those mailed in tax returns were sent to what, only 5 or 6 regional IRS centers with a generous 4 1/2 month deadline before "all the results are in." Mail in ballots have to go a gazillion county election offices to be handled by a bazillion county election officials, all of whom are currently on a very short deadline to get those ballots counted.