Why is it so hard to predict which teams will make the Men's College Basketball Final Four?

Unlike other sports where playoff rounds can be a series of multiple games (such as the NBA, NHL, MLB, etc), the "March Madness" college basketball playoffs features single elimination games for each round, so in a one game playoff, upsets are much more likely than in a 7 game series, where the statistically better team is most like going to win. So, out of the 68 teams that make the tournament, it is hard to predict who will each round.