Your forgetting that a "natural orbit" has a safer failure mode. With the powered orbit, if the engines fail, you fall. In a natural orbit, if the engines fail, you continue to orbit.
Using a powered orbit would be like parking your car on a hill by putting it in gear and revving the engine just enough to keep the car from rolling away. Better to turn your wheels to the curb and engage the parking brake.
I would imagine (as that's all we can do) that powered orbits would only be used as needed. Natural orbits would be standard ops if not.