Maybe some people don't feel qualified to make a decision?
I have said this before, but one amendment I would love to do to all democratic countries is increase the voting threshold required in legislatures based on the inverse of the turnout. If people don't rock up to vote, politicians need a greater majority to pass legislation. Therefore if the electorate isn't happy with any of the political parties, they simply don't vote and political parties have to either start working together or be forced to do nothing.