I am not sure I can answer because I don't know what you mean by "desire to service something larger than themselves"?

Are you referring to his love and need to be monogamous? Why would I have to serve that as a 'greater purpose' than serving what I need to make me happy? Is serving what makes HIM happy a greater purpose?

Maybe I misunderstand to what you refer as 'something greater than'... [myself].

You mentioned enjoying oneself- as if you think that is all people in polyam relationships do. I and many other polyamorous people work very hard at our relationships; maintaining them, supporting our loves, being committed to growing and changing over a lifetime together. Polyam relationships can be many things, including endearing long-term lifetime fulfilling relationships.