I think the general principle is that societal decision makers should be roughly representative of the people whose lives are impacted by the decisions. Of cou

I think the general principle is that societal decision makers should be roughly representative of the people whose lives are impacted by the decisions. Of course it's possible to take this too far. As for why race and gender are considered important, I think it's probably because they are easy to measure, and there has been a lot of discrimination. Most of the other demographics are probably pretty evenly represented? I've never heard of someone getting passed over for promotion or housing because they were left-handed. The city/country split is a good point. There is some provision for that in many political systems, with different geographical regions being represented based on population, but it's far from a perfect system.