[matthewmacleod]

Why does some field need to mirror racial/whatever composition of the society?

If it doesn't, then it's pretty suggestive that there's a wider problem. Why do people from different backgrounds not enter that profession? Are they being discouraged somehow, and how can that be avoided?

Diversity is an self-evident good, in that multiple backgrounds and experiences result in a more well-rounded team. Trying to make sure you have that benefit is good sense.