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...the umpiring in baseball may be of poor quality, but individual official rulings rarely have the power to change a game all by themselves...this puts more power in the hands of the players. For example...if you have an ump with a huge strikezone...yes, that twists the outcome of the game toward one with few runs scoring, but both teams have time to adjust their play to account for this.
Soccer is much easier to "fix" if you're one of the refs than any other sport.