I have to admit, that seems like a strange question to me. The majority of the economy, and the majority of transactions have nothing whatsoever to do with the government. Why would you think that government spending would be the only reason money might need to be created?
It is created to allow the economy to grow. It would be created anyway, even without a Federal Reserve or Central Bank of any kind, simply by virtue of fractional reserve banking. But with a central banking system, you have someone at least trying to control that growth some. The Federal Reserve doesn't have total control over the creation, or non-creation of money, but it does have tools with which to manipulate it.
Personally I prefer this system, to one without a central bank, or to one in which there are no banks (or banks have to keep 100% reserves, and therefore people actually have to pay for the privilege of keeping their money there), in which the money supply is controlled entirely by a few politicians or bureaucrats. As it stands, the market has a large say in determining how much money it needs for it's activities, but we have a group at least attempting to "mind the ship" and keep things under control. How good a job they've done of that... that's another debate entirely.
There are certainly other structures and ideas for how a central bank could be set up, maybe some of them would be better, or maybe we really would be better off without a central bank of any kind. I'm just trying to make clear how the system actually works, and why it doesn't inherently have to lead to ruin and "slavery."
It certainly has it's pitfalls and disadvantages, and I'm not necessarily trying to argue that there aren't other possible systems, or that others might not actually work better (though honestly every possible monetary system has it's own advantages and disadvantages, so it's really just a matter of what you're willing to risk/give up, and what you think you'll gain. Also since all of them would be administered by humans, any of them COULD be royally screwed up). I'm just saying that there is a logic to the current system, and it doesn't by necessity lead to ruin and destruction.