The gun is not used unless the life of the officer or the life of another person is in danger. It is therefore not fired unless deadly force is reasoned. You never fire to wound. If the person is a threat, he or she is armed. A wounding shot to the leg or arm would allow them to get off a shot. That shot could end someone’s life. If they have a weapon other than a gun, the same rule applies.
As for being accurate, police departments demand their officers go to the range and accomplish certain minimal scores to remain active on the force.
If I’m a police officer, I don’t want another officer being on the street with me, that would not be able to stop someone trying to kill me. My life depends on their ability to shoot accurately. Their life would depend on me being able to shoot accurately.
Did I perhaps see you on such a range on a Saturday in a dirty, little city, long ago? If so, there were only two of us who could put most of the 50 rounds in an area about the size of a coffee cup on the target. The range was insufficient, and so was the training.