Companies get an overview of fleet management movement with GPS tracking. They can optimize the routes and it helps to put a complete stop to company car misuse (e.g. personal travel, speeding). Cost savings will take effect immediately after installation. Next benefit is the special features, such as driver identification. Also, GPS tracking is often used by car rentals or taxis.
They usually use GPS car tracking combined with the log book. The vehicle logbook can be required by tax office if the car is used for business.
Besides an owner overview of mileage, GPS tracking is ideal in car borrowing (for example to the young driver). From the protection against theft, it can play a facilitating role in finding the stolen car (LoJack system). GPS locator does not actively report the theft, but it can help with finding the stolen car.