It's called Capitalism.
Those who control the means of production hold on to nearly all earnings and release as little as possible to labor. In most parts of the country, there are very few opportunities for skilled labor. Thus, nearly everyone is limited to employment near minimum wage.
"Right to Work" laws undermine unions and most jurisdictions won't set minimum wage about federal levels.
You can thank the Republican party, who keeps unemployment low, but at the cost of real wages.