The answer is: emphasizes the self-interest of decision makers and voters.
According to the theory of public choice, the legislation that will be passed by the government will be influenced by the ever ending battle between self-interest of decision makers and voters.
To maintain their position, decision makers have to appeal to both the general voters and the organizations or interest groups that fund their campaign. Often time, both of them do not have aligned interest with one another. This will create a constant conflict between decision makers because they have to choose which side should they please the most.