In any society it can be difficult to change traditions, rules, or beliefs that have been in place for a long time. This is especially true when no one questions them or the reason they are in place, which is the case in The Giver. The members of the community do not question the rules and therefore are not motivated to change them.
Aside from Jonas, we really do not see anyone else in the community questioning the rules. It is only after Jonas so vehemently reacts to the video of his father releasing the newborn and then refuses to go home again, that the Giver realizes things must change and he needs to do anything he can to help facilitate that change.
"having you here with me over the past year has made me realize that things must change. For years I've felt that they should, but it seemed so hopeless" (CH. 20).
The Giver has felt this because he knows so much more about the world and about how the community used to be prior to Sameness. The other members of the community do not have this knowledge, however, so they have not become "hopeless" about the current situation and its inability to change. It is only with knowledge, the kind that the Giver and Jonas possess, that the members of the community can begin to understand a different type of world without the rules they currently live under. Without Jonas escaping, the rules probably would not change because there is no motivation for the members of the community to change.