Money buys politicians, which buys elections which buys what they do/don't do in congress. It's all an organized but legal crime syndicate. Extortion, bribery, etc are legal in politics, because politicians make the rules.
In other words, politicians run legal protection rackets. Mafias.
http://www.businessinsider.com/major-study-finds-that-the-us...
> Researchers concluded that U.S. government policies rarely align with the preferences of the majority of Americans, but do favour special interests and lobbying organizations: "When a majority of citizens disagrees with economic elites and/or with organized interests, they generally lose. Moreover, because of the strong status quo bias built into the US political system, even when fairly large majorities of Americans favour policy change, they generally do not get it."