That's because people look at aggregate wealth in America as just that, like some fixed amount that somehow is divided up disproportionately among the masses.
I think it's funny when people gripe about how much CEO's make, like somehow their salary is a game changer to amount a company has to pay it's low income earners. Most of the large companies of the world like Starbucks, Exxon, etc employ tens of thousand of people. If you took the millions that the CEO made (we are talking top of company here) and divided it up among all the employees within the company, they would make about $200 more a year.
When it reality wealth has always been along the lines of a ever expanding stream of revenue and that doesn't always mean that someone is getting cheated. Some do move up and some stay in the same bracket. But the idea is continuously expand your own stream of wealth and not look at what you have in such a "me vs you" way. I'm going to label myself A while I label you B. and we'll fight over semantics while ignoring what we are doing to get ahead.