Why not?
-Humans are easily overwhelmed by choices
-Humans are easily overwhelmed by information
-Humans don't have the information they need or the time and resouces to gather it
-Humans routinely make poor decisions even when they have good information
-Humans are lazy by nature
-Humans are not rational actors in their own self-interest as economic models assume
-Humans are not as intelligent, on average as economists who assume that other humans will make decisions like they do.
Once again we see the wishful thinking of conservative dogma running headlong into the pillars of human nature and getting knoocked back squarely on its ass.