In The Giver, certain duties necessitate isolation. To gain knowledge and wisdom, for example, is to separate oneself from those without such abilities. This is in part because learning requires solitary reflection, and in part because it's hard to identify with anyone who doesn't share the same wisdom. Being isolated also increases the pain of suffering; with no one to share the weight, the burden is that much greater.
Jonas is only able to form close bonds with the very young or the very old because they, too, are exempt from the community's restrictions.