But, as has been said before, if the authorities had banned driving how could I expect the rental company to help me?
Its a poor example as you are not renting an aircraft to get yourself to a destination, so a comparison is not equivalent. You are effectively paying for a company who just happen to have aircraft at hand, to provide an all in service to some distant point. Thats not the same as renting an aircraft. They can rent you an aircraft, but its not their fault that you will not be granted takeoff and thats not the rental company's problem.
However if say a ban on driving were introduced, and you had booked a chauffeur service, you would insist that the company provides you with suitable alternative means, such as a mix of bus, coach, air, or rail transport.
There's a difference between buying a DIY product and paying for a full service.