Popular art reflects the culture from which it sprang. It is this basic fact that underpins the concept that representation in the arts is important. How people of all types are depicted in the arts both reveals the cultures attitudes towards those people and how those people see themselves within the culture at large.
In my book there is a world of difference between representation and bean-counting. The latter is simply plugging is a person of X characteristics to simply say that those characteristics are in the work. Bean-Counting takes no notice of character, reducing people to tokens for fulfilling quotas. Representation is about having characters realized to your fullest ability who happen to encompass a broad range of traits and characteristics. Both require conscience effort on the part of the artist but one makes for better art and more honest representations.
Representation matters because art effects those who consume it. Not only the dominate member of a culture but those who are not in positions of authority or respect. People internalize the depictions that they are exposed to and those internalizations warp the self-image and behavior of all who take them in.
Representation matters because without it we have a terrible waste of talent and resources. We need artists of every stripe participating in the communal village. Even voices you do not agree with, particularly voices you do not agree with. There was a time when the concept of individual rights was the dangerous new idea that the old order tried to extinguish. What uplifting and revolutionary thought is waiting out there?