This is just the utility model. It's nothing particularly nefarious. Consider what your electric utility, your water utility, etc. do. If you use more, you pay more. If someone comes around and hooks up a garden hose to your outside faucet and steals your water, or plugs an extension cord into your outside outlet and steals your electricity, you still pay. Unless you can catch the thief and make him pay.
Funny enough, the utility business broadly wants to move away from this model to more of a cap-based prepaid model. Where I live, to get on the standard payment system may require a quite hefty deposit up front, but the prepaid payment option does not. I get the impression that, if not for customer sentiment and inertia, this would be the default option.