I can see it with gas cars because they then have to have someone drive it to the nearest gas station and fill it up, which even for an airport with an on-site gas station probably would be at least 20 mins, possibly more.

But with an electric car, they just have to park it (which they have to do anyway) and plug it in (although I suppose if you left it near zero, it could mean they can't re-rent the car for some amount of time).