Given that people are interested in range, then
distance per capacity (miles/kWh ... km/kWh) would seem the correct method surely?
The calculation is easier when knowing the usable capacity of your battery.

(Mile or km per kWh x Capacity = range. Doing it the Metric way is a more-convoluted calculation)
And? Is that a problem?
Lets say my car in todays road and weather conditions uses 190w/km (19Kw/100km).
Lets say I need to drive 213km/132ish mls.
That is 190x213=40470w or 40,47Kw. Or roughly 60% of my cars battery capacity.
To be honnest in this case a qiuck one would be 200x200=40000Kw or 40Kw if you wish.
The thing is I can read the 190w (watt/km) out of the spedo screen as 19Kw/100km in metric it's dead easy to scale down to 190w/km, then it's a matter of multiply by the distance I intend to drive, in this case 213km.
I set my the useful capacity of my car to 61Kwh or rather 60Kwh for quick calculations, so about 75% should give me enough range to do the trip if the roads are reasonable flat and my consumtion does not go much up because of head wind.
When taking about the non linear % of most EVs, I calculate % in the MG4 with 64Kwh battery like this (rule of thumb):
1/3 of battery capacity is 40% ish (20Kwh).
2/3 of battery capacity is 75% ish (40Kwh).
3/3 is offcourse 100% (not ish). ?
Of course, this is very roughly calculated, but this is much closer to the truth than 33.3% 66.6% etc. In any case this is more than good enough for daily use and as I get to know my car better, I can adjust those ishes closer to reality if needed.