If I ask to generate an image of a couple, would you argue that the system's choice should represent "some ideal" which would logically mean other instances are not ideal?
If the image is of a white woman and a black man, if I am a lesbian Asian couple, how should I interpret that? If I ask for it to generate an image of image of two white gays kissing and it refuses because it might cause harm or some such nonsense, is it not invalidating who I am as a young white gay teenager? If I'm a black African (vs. say a Chinese African or a white African), I would expect a different depiction of a family than the one American racist ideology would depict because my reality is not that and your idea of what ideal is is arrogant and paternalistic (colonial, racist, if you will).
Maybe the deeper underlying bug in human makeup is that we categorize things very rigidly, probably due to some evolutionary advantage, but it can cause injustice when we work towards a society where we want your character to be judged, not your identity.