Assume that you have something that has a complementary relationship with something I have, but doesn't have a complementary relationship with anything you have. Assume that I'm in the same situation in relation to you. If we trade objects, we both benefit. Hot dog buns and hamburger buns are designed to be complements of certain respective forms of ground meats, hence the naming scheme.
Aesthetic value is still value. Most people would prefer not to eat Nutraloaf three meals a day.