When a small group of people control a disproportionate share of the resources of a country, they're able to use their wealth to shape laws, policies, and institutions to their advantage, allowing them to control an ever greater share of the country's wealth, while insulating themselves from the repercussions of their actions. Eventually, as the productive part of the country's population is forced to shoulder an ever-greater burden, they begin to question why they are doing the lion's share of the work, while another group of people get to enjoy its benefits. Aside from the inherent immorality of the situation, it's economically unproductive, unsustainable and inconsistent with democracy.