I've had several situations in the Mountain West when roads suddenly closed <25 miles away from my final destination (and fuel). Some of these required upwards of 100 mile detour on rural roads with almost no civilization. That detour was not part of the original range calculation. For an EV the detour may not even be an option, you have to go backwards to a major highway to find a charging station that may be in range.
Hell, I've nearly come up short in an ICE vehicle a couple times. I try to keep 150-200 miles of spare range on my vehicle when I am in that kind of country. That is hard to do on a typical EV.