I haven't driven a car in the past 15 years that didn't have a "distance to empty" option on the dash.
And I haven't driven a vehicle in the last 15 years that has such a feature. But then all I've driven in that time is a basic light pickup and a Jeep. I know range features are available, but they're more common in higher end domestic or import passenger cars.
Anyway, MPG's a useless metric for figuring out whether you need to stop for gas, unless you also know how big your tank is. If you do, then you're doing the math in your head to duplicate the distance to empty calculation on your dash.
Why would someone not know how big their tank is? There should be a clear reminder of the size every time you fill up.
Finally, the portion of the population who routinely take drives with >150 miles between gas stations is tremendously small.
There are quite a lot of people who live in the western US and Canada, where this is true.
Not that my anecdotes best yours, it's just that there would need to be conclusive evidence that a change would be worth the expense incurred and the arguments for gpm style fuel efficiency ratings don't seem (to me) to be compelling enough to justify such an action.