By and large, people are lazy and don't want anything more than a choice between A and B, despite the regular complaining about the fact that we only have two viable parties. In all this time, not one 3rd party has done the work to elect local and state candidates, and build the necessary infrastructure to plausibly compete. They always pop up every four years to run a promotional candidate with no chance of succeeding without having done any of the ground work to make their party viable.