German here. Indeed only the driver of a car is punished for speeding. The burdon is on the officials to determine the driver. But they will send an official inquiry to the car owner to name the driver of the car, if the identification is not obvious by a photo. There are cases where no one gets the ticket, because the driver is not named by the car owner, sometimes for very valid reason. With a larger group of people having access to that car, this can be true. As a consequence, sometimes people get off their ticket.

There is a catch however: while you might get out of a ticket once or twice, the authorities can order you to keep a drivers log in the car. That means, a written log of every single drive has to be kept. So that there is never any ambiguity of naming drivers going forward. And having to keep logs of all your drives going forward is something you really want to avoid.