Jeff, I agree with you which is why we need reasonable redundancy in the cockpit. The probabbility of my EFIS and my Garmin 496 going down simultaneously is just about zero. I can get down to an airport solely with my 496 no problem should my EFIS ever quit.
I know you can buy an internal GPS for the AFS boxes and save some money, but then you really would have all your eggs in one basket.