Bureaucrats want bigger bureaus. Special interests are interested in whatever's special to them. These two groups bring great pressure to bear upon politicians who have another agenda yet: to cater to the temporary whims and fads of the public and the press.
P. J. O'Rourke (2007). “All the Trouble in the World: The Lighter Side of Overpopulation, Famine, Ecological Disaster, Ethnic Hatred, Plague, and Poverty”, p.197, Grove/Atlantic, Inc.