Then of course the more money you have as a society, the more money the rich people of your society will have. And if you have a large population, the difference between those who are rich and those who are not is gonna have to be very large just because there's so much more money to be divided between the necessarily few rich people (again: if many people have lots of money then you don't have a special class of "rich").
So to summarise, if you're gonna have a rich society, you're gonna have to have rich people who are much more rich than not-rich people.
Problem is, that's not about inequality, nor about the richess of socieities, but about amibition. You see, everyone wants to be rich. Translated: everyone wants to have more than almost everyone else. So everyone supports an economic system that supports rich people, and therefore, wealth inequality.
Which is funny because the vast majority of people who support that kind of system are necessarily going to have to be not-rich.
So in order for most people to be able to dream that, one day, they'll be filthy rich, most people have to spend their entire lives in relative (or absolute) poverty.
Funny old world, eh?