You _can_, but if I have a reservation a week in advance, then it’s not much use. Someone could return the car with no batter at 3:15, for my 3:30 reservation.
Here, there are many more cars, but it's not possible to reserve far in advance. You can reserve for free for enough time to walk to the car (20 minutes?) or pay to reserve for longer.
The charge state is shown prominently.