This might stem from the simple fact that the average American is constantly getting screwed. It's just a sliding scale of how badly.

Both parties are against them, owned by oligarchs and mega donors that are actively trying to increase the wealth gap and make average Americans fight each other over the petty dilemma of the week, rather than the real fight of the whole country vs maybe a couple thousand ultra rich douchebags.

When is the last time the American government didn't screw at least 70% of its voters?