The game moves so quickly, and combined with the pressure of the crowd to influence any decisions they make, it’s easy to slip up and miss some basic calls.
Having said that, if fans expect players to be at their best, then it’s fair to expect referees to also be at the top of their game.
What’s troubling is that this postseason has been especially filled with critical referee errors at crucial points in the games. The league supposedly utilizes their best officials to work postseason games, and yet the referees who are apparently the best in the world at officiating basketball games are consistently missing key calls at important moments.