I don't ever think I would choose to display percentage left for my battery - how are you supposed to figure out how far you've got left without some complex mathematics factoring in many variables. Miles left is easy to work out.
The problem is the miles it says you have left are just as risky to rely upon. The remaining miles display is a BMS calculation based on a hardcoded efficiency calculation.
Say the car said you had 275 miles remaining, so you set off on a 250 mile journey thinking you have 25 miles to spare - but it starts raining heavily, and you travelled at night so the lights are on, and it's still a bit warm so the A/C is on too. Oh and you're in a hurry too, so you're not exactly hanging around. The result is that you're not going to travel 275 miles before needing to charge, and you might not even travel 250 miles.
Because percentages will go down slower than miles (because it's not a 1:1 relationship) you could plan a journey based on getting to the destination, or a charger, at a certain percentage level. Also, from a purely psychological level, I think it is better to plan to get to a charger at X percent rather than the car telling you that you have 50 miles range, planning a trip to a charger that is close to that, and finding you can't make it or that it is nerve wracking doing it.
Also having it on miles leads people to constantly fret and obsess about why they aren't getting the WLTP ranges, why the reported range is less than it was yesterday at the same charge level, etc. Driving an EV, in my opinion, is about having a sense about how far the car can go on a full charge in ideal conditions, and planning journeys and charging etc accordiingly, without relying on explicit "remaining miles" calculations.