I definitely get your point, but let's look at it from another direction. Do I also need to install a tracking device in my car now that you can buy one or should that still be optional? They will probably be standard one day. Your idea is not completely implausible, though only one person, (maybe husband/wife or whatever), being able to drive any given car would present problems, but it would have to be phased in over a long period of time.
Not really a bad idea, I just question the practicality and fear the misuse of the information given over to "them". Anyway, it looks like at least 5 people total are still reading rather than my estimated four. ;-)
Pat