I call this the L-Curve . Income is not the same as wealth. Most of us are consumers. We consume our income almost as fast as we earn it, with little reserve. The very rich don't spend very much of their money on consumable goods.
Wealth generates more wealth.
A curve representing the distribution of wealth is far more lopsided than the distribution of income. The bottom half of the population controls almost nothing. These quotes are not really inconsistent. You should care because extreme differences in wealth create extreme differences in power, and that distorts democracy. For example, if you want your voice heard in regard to a social or political issue you can write to your congressman or write a letter to the editor or take up a picket sign and pass out leaflets.