I remember hearing that it was based on market research that a significsnt number of people would pick up coffee on their way to work/home, and drink it once they got there. So they superheated the coffee so that it would be at its ideal taste/temperature when they got to their destination.
But the refill thing sounds much more likely
You just gave me enough punchlines to last a lifetime! Why would I need to buy volume 2 at all now?