If the rings were reversed, (i.e.: small ring on the outside and the large ring on the inside), and the cassette left as is, (i.e.: largest gear inside, smallest gear outside), and you did not want to cycle with the chain running from the inside ring to the outside gear, nor the outside ring to the inside gear, you would lose the use of your lowest gear combination and your highest gear combination. I for one want to use those two gear combinations!

Ride on! -Spoke