I looked into this a little, Pennsylvania says it's because of counting mail in ballots. But of course they're planning on going against the Supreme Court ruling to not count ballots that don't have the dates in the correct place.
Georgia is not going to have to count ballots, which is what I thought was going to take additional time. And I got pulled away and didn't get to Michigan.
Oh and in this election republicans are going to watch the ballot counting, and the pandemic is over, so it can be done properly.
With all that hopefully there'll be less of what happened last election.