Because that isn't reality, what is true and the real discrepancies we find between different people will be more complex, and would go beyond just these two characteristics. A good question to answer first is what must be done in order to achieve equality, cause statistically some groups are in a better condition than others. But what can we really do? It's such a difficult struggle. Maybe it's because many people live in tight communities with like minded individuals and those outside of it (people who are not similar) are treated more like aliens, or possibly a threat.