There's a difference between some people voting by mail and tens of millions of ballots being posted all over the country with a complete disregard for the accuracy of where they're being sent and how many people are receiving.
My wife received 4 in total, I received zero and 1 for a former owner of the house (I think..not even the last owner if it was).
10 months ago it was made clear that this was going to be a problem and that people wouldn't accept the result due to the high cases of potential fraud to create and disregard ballots.
Voting in person, on paper, Infront of people is the only way to secure a vote. The further you move from that, the less credible the results become.