A jump starter can be used on a vehicle for several reasons, including:

To jump-start a dead battery: A jump starter is designed to provide a quick burst of power to a dead battery, allowing the vehicle to start when the battery has lost its charge.
To avoid calling for assistance: A jump starter eliminates the need to call for assistance when a vehicle won't start due to a dead battery, allowing the driver to jump-start the vehicle and be on their way.
To save time and money: By avoiding the need to call for assistance, a jump starter can save time and money, as well as the hassle and inconvenience of being stranded with a dead battery.
To be prepared for emergencies: A jump starter is a convenient tool to have in the boot of a vehicle, providing peace of mind and a reliable solution for jump-starting any vehicle in case of an emergency.

Overall, a jump starter is a handy tool to have in a vehicle, providing a quick and convenient solution for jump-starting a dead battery and avoiding the need to call for assistance.