One reason is our state of permanent war. Wars as envisioned by the bright minds of the Pentagon bureaucracy and the best Congress money can buy don't come cheap.
In 2009, The Washington Post reported that the war in Afghanistan was costing two billion dollars a month ("Obama Plans More Funding For Afghan War", Karen DeYoung, 2009-03-27http://www.washingtonpost.com/wp-dyn/content/article/2009/03/26/AR2009032602135.html). Gosh, if Afghanistan has a population of 28.4 million, that means the U.S. could just give every man, woman, and child in Afghanistan $70/month or $840/year. That's pretty damn good for a country with a gross national per capita income of $250/year (http://www.unicef.org/infobycountry/afghanistan_statistics.html).
Ironically, many of the deficit hawks are for a "strong defense", but against foreign aid and taxes.
A second reason is that we vote for Congressional candidates who will "bring home the bacon" to our districts. Alaska is home to a large number of anti-tax people, but Alaskans get more per capita in federal money than in any other state. Isn't bacon another form of pork?
Or maybe it is that not enough of us vote. If 25-40% of the registered (or eligible) voters don't bother to show up, we are going to have candidates elected by a plurality rather than a majority. And we are going to be left with candidates who either want to spend a gazillion on wars and pork or want to spend a gazillion on social programs and pork.
