Of all the problems people face in the modern world, why isn't wealth inequality at the top of that list?
For a millionaire or a billionaire to have the excess of money that they have, there has to be a lot of people who don't have the money hoarded by those millionaires and billionaires. Consider the following extreme. There are 100 people, each of whom has 1 dollar with which they can buy a loaf of bread for 50 cents which should last one week. There is one person who sells the loaves of bread, so after the first week, that person has his original dollar plus $49.50 more. He now has $50.50 while everyone else only has $0.50 dollars left. The man who has $50.50 is the richest person (relatively the millionaire or billionaire of the group) while the other 99 people only have enough for one more weeks worth of bread. As simple as this example may be, it can be extrapolated to the economies most people face today as the wealthy or one percent earn a greater percentage of the income available every year.