A responsible employer checks certificates of insurance before paying any mileage. Mine does.
Who's to say mileage would be paid?
If they're talking about teams who cover multi locations as standard then it may not be that people even have a home location?
And it still doesn't cover what would happen to the large number of workers who don't have their own car. Some also cycle, walk, get lifts or get the train. I don't see how they could be treated differently to someone with a car either.