Who doesn't know this situation? You have to go from A to B and no plan of doing so.
Reasons for such a stupid situation can be manifold:
Maybe it was not possible to book a ticket for a plane or railway or you managed to get a ticket but an official strike made it impossible to use it.
Let's say you live in Augsburg and your job is in Munich.
Everyday you use a train to get there and back home but today the train will not move a millimeter because of an official strike.
You need to get to work due to a very important meeting. But how?
Unfortunately you don't have a car and to ride the whole way by bike is impossible.
Legally, you are obliged to appear on time at your job - no matter how! And your boss is not very sympathetic!
You could call the car sharing agency and hope that sombody wants to drive right this moment from Augsburg to Munich.
Forget it! Calling friends and ask for help? Maybe, but not very promising! Then you have the idea. The car rental! You explain to them your situation and you can even choose from different models.
You show your driver's license and identification card before signing the contract and the necessary insurance is already covered.
You get the car with a full tank and have to give it back with a full tank. Simple and fair! Apart from general fees, insurance, and gasoline you have to pay a certain amount for the mileage. That's all.
And in case the strike is over and it is possible to use the train after work you can leave the car in a branch of the car rental agency in Munich. That's service!