The computer suffers no such problems. The human brain is easily stressed out by events and loses effectiveness when tired. Emotions blur the human brain's capacity to make clear, logical decisions, even when they are thrown before its eyes, and impair problem-solving capabilities. Age also has a devastating effect on the function of the human brain. Once senility sets in, the brain is of little use to anyone, and the person becomes a liability.
Computers are far from perfect themselves.
Computers have only a limited capacity for learning and even this usually is not entirely accurate, for the computer lacks the common sense of the human brain, thus it cannot accurately realise its own mistake, if any.