There are many 'special people' in the world who we may see only occasionally but who are important to us. They may not even be good friends. But they are an important part of the whole picture.
This is a special type of relationship. Neither party seeks to change it. A niche has been established and is tended as such.

People who live rich lives have a skill in maintaining a wide variety of relationships and looking after these relationships. They have a wide repertoire of possible relationships and so can enjoy each of them. People who have only a limited view of relationships have a limited life.