Personally, I think the “wealth gap” statistics are pretty much self-explanatory–concerning the ever-widening “Gap Between the Middle Class and the Rich.”
Differing levels of wealth directly translate into many “quality of life” differences between classes (for lack of a better term)–such as–less disposable income, lesser funds for housing, lesser funds for retirement, lesser funds for heirs (if you so choose).
I’m sure there are more examples, but those are the most significant, life-changing issues in my opinion, and, most likely, why it is referred to as the “wealth gap.”