According to The Giver, why did Jonas have to receive and store memories of pain?

According to The Giver, as the next Receiver of Memory, Jonas has to receive and store memories of pain so that he can gain wisdom.  Without wisdom, he would not be able to "fulfill his function of advising the Committee of Elders" when he is called upon to do so.  Whenever the Committee is faced with a problem with which they never have had to deal before, they seek the advice of the Receiver, who will use his memories to tell them what to do.  They do not want to hear about pain themselves; "they just seek the advice". 

Upon receiving this information, Jonas wonders why everyone can't have the memories, because it would seem to be easier for the Receiver of Memories if the remembrance of pain in particular could be shared.  The Giver then explains "the real reason The Receiver is so vital to (the people), and so honored".  If everyone shared the memories of pain, then "everyone would be burdened and pained", and the people did not want that.  To spare themselves the suffering, they chose long ago to select one person - the Receiver of Memories - "to lift that burden from themselves" by bearing the weight on his own, in their stead (Chapter 14).