The first is simply to show respect and filial piety to the man who founded North Korea half a century ago and ruled it virtually as a god ever since. Though he was often condemned as a dictator in the West, Kim Il Sung seems to have been revered by many North Koreans, as even defectors usually acknowledge.

''Kim Jong Il needs his father, needs to wear his father's jacket,'' said Han S. Park, a scholar of North Korea at the University of Georgia. Mr. Park said that in time Kim Jong Il may gradually emerge and rule more openly on his own.

The second reason Mr. Kim may have been reluctant to take on the presidency is that it would make him a far more public figure and would oblige him to meet ambassadors and foreign visitors. He has always been an intensely private figure, a man who virtually never travels or meets foreign visitors.

Under the new Constitution, the tasks of receiving ambassadors and representing the state for diplomatic purposes will be taken over by the president of the presidium of the Supreme People's Assembly, the legislature. The president of that presidium will be Kim Yong Nam, the previous Foreign Minister.

Kim Yong Nam, who is not related to Kim Jong Il, is now ranked No. 2 in North Korea's hierarchy.

It is not clear why Kim Jong Il is so reluctant to meet foreigners and appear in public. But a top North Korean official who defected to the South, Hwang Jang Yop, has said Mr. Kim believes that he derives some charisma or power from the air of mystery that surrounds him.