It is a long process to change a rule in the community. First, a change to the existing law is proposed. Next, a committee analyzes the information about the rule change. It is indicated that the process that the committee goes through is a long one:
They said that the committee members would become Elders by the time the rule change was made (The Giver, Chapter 2).
If the rule is an unimportant one, the committee eventually decides on a change. If it is an important rule that will have a large impact on the community, the Receiver then analyzes the request. Of all the Elders, the Receiver is the most important one. He has much more knowledge and wisdom than the other Elders.
Even for less important rules, the committee can spend years studying, discussing, and a making decision. Sometimes it takes so long that everyone forgets that a change had even been requested.
The long, multi-step process is the reason why it takes so long. This stems from the reality of life in the community: the society is closely controlled and regulated. Rules are intentionally made to maintain this order. No one is allowed to stray from the regulations put in place by Elders and committee members.