Easy cooling
The easiest way to cool is with airflow. But for high power applications, air cooling will not be sufficient. With air cooling, you are dependent on the ambient temperature and the airflow. Even when these are optimal, it will still not be enough to cool the batteries sufficiently.
In high power applications, a more effective cooling system is required to keep the batteries within the optimum temperature range. Air cooling alone is often insufficient to remove the large amounts of heat generated during charging and discharging of the batteries.