To rip off the US tax payers. It probably benefits the people who own the banks that issue the loans of currency and the defense contractors for a start.
The government is only a puppet of the real power brokers who control the money.
Try this link for an in your face rundown for those that want to stick their heads in the sand. Can't say it any better than this guy.
http://www.youtube.com/watch?v=yqmGaWzI0zQ
