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It was adopted in 1957. Before then, everyone just thought, "oh, he made an effort to hit the ball, let's give him another chance." But then in one game in 1957, Gil McDougald of the Yankees swung at a ball and missed and Rocky Colavito of the Indians screamed to the umpires, "Wait, that should be an out." The umps responded with, "But he tried," to which Colavito said, "But that's stupid, it's his fault he missed."
That very moment, Rocky Colavito not only became the Indians captain, but changes baseball forever until 1976, when Davey Johnson asked the rule for no swing-and-a-miss strikes was reinstated, which the league granted for four days until they realized there was no reason to listen to Davey Johnson.