Why is The Receiver the most honored position in Lois Lowry's The Giver?

The Receiver is the most honored person in the community because it is a unique position only one person can hold at a time. This position requires a person who has some very unique traits. When Jonas is selected, he knows almost nothing about the Receiver except that he is an old man with a beard who almost never attends community functions. 
At his Ceremony of Twelve, Jonas learns the Receiver of Memory is selected because he or she has the traits of courage, wisdom, integrity, intelligence, and something called the Capacity to See Beyond, which is an almost supernatural power to receive memories.
At first, Jonas doesn’t think he has this power. Then, he understands why he thought he saw an apple change, and why the faces of the crowd took on a strange dimension. Jonas accepts his assignment.

"I think it's true," he told the Chief Elder and the community. "I don't understand it yet. I don't know what it is. But sometimes I see something. And maybe it's beyond" (Ch. 8).

The community has other reasons to treat the Receiver of Memory with honor. The Receiver stores the community’s memories, which are the community’s collective consciousness. These memories are important because the community itself has no sense of history. When making decisions, they rely on the Receiver. Without him, they will repeat past mistakes. They do not want to be burdened by their history, so they ask the Receiver for advice. 
The Giver, Jonas’s mentor, explains the community does not have to take the Receiver’s advice. 

"I have great honor. So will you. But you will find that that is not the same as power” (Ch. 11).

The Giver explains to Jonas that when the community asked him if they should add to the population, he advised against it because he alone knew what hunger, war, poverty, and death looked like. It was ultimately up to the community Elders to decide. The Receiver of Memory is the community’s most painful position because it is one of immense knowledge but no power.