Swing states. Controlled mainly by Republicans pass draconian voting laws before 2020 election saying mail in votes cannot be counted until after the close of polls on election day and only after election day votes are tabulated.
You were warned well ahead of time about red and blue "surges" as the votes were being counted. You were also warned that because of voting laws in several swing states, it would take a few days to declare a winner.
Much as I am loathe to admit, take a look at Florida and Texas. Deep red states that both allow mail in voting. They tabulate their mail in votes ahead of the open of polls on election day. So their results are available that night or early the next morning.
I can't stand either one of these states for various other reasons, but when it comes to counting the vote, they have their shit together.