Impact across a broader spectrum creates varying levels of individual importance. This creates a natural hierarchy . In the case where a person is a 'single poly' for lack of a better term, and basically has the same level of involvement with multiple partners then I would imagine their perspective would be different than that of a person who is married with kids or a house and other joint endeavors beyond a romantic conection.
Hierarchies exist everywhere in the world. Why would relationships be any different.
Playing the Game of Life with Monopoly rules.
Monogamy might just be in my genes
Poly Events All Over