Yeah but your fantasy trip thru Arizona ignores the reality that the person you are responding to has to live with. If you had been driving your 60's vehicle at this time of year in the salt and slush of Chicago it would be falling apart from rust. The point being made is that if the car has a limited and predictable life span due to external rust there is little point in worrying about internal corrosion that will not eat the car as fast as the external corrosion will.
-jim