I think you miss understand the magnitude of them problem. If a GPS tells people to drive a road that is only good for 4x4, regardless how smart the person is, he/she will be lost in the wood. It has happened many time.
And you seem to neglect the simple counter argument. Yes, stupid people did not increase, and yet, if the product is not stupid proof, it will soon be replaced with something that is stupid proof.
Well, it is not that people are actually stupid, they are just smarter to find a case where your assumption no longer hold true. And they will get into trouble when your solution is flawed.