Money is heavy

It is difficult to move significant quantities of money from one pocket to another. Say, for example, you are the United States and you have a few thousand moldy million lying around, and you (or at least your leadership) wants to give it to good buddy Halliburton. People would look askance if you just handed it over directly. So you go find a small country that is ruled by an evil dictator, who is also an infidel. It helps that this evil infidel dictator is already killing his people pretty much on the whim of the day. You start a war, move in, and take out the evil dictator. Because he is already killing people, your actions fit well with the principles of compassionate conservatism, putting a lot of them out of their misery more quickly and liberating the rest. Also, because he is an infidel, you look like a crusader. Then you set up a new government that looks wise and experienced, but which, in fact, has no understanding of western-style cost accounting. You give them the money, and you let Halliburton send them invoices. They pay the invoices, money changes pockets, and you are a hero.