Firefighters work together as a team called a company. Everything they do during their shift must be done together so they are always near their fire engine, and always ready to respond to an emergency. It is very common for a company to receive an alarm while away from the fire station or while returning from an incident. All units are equipped with GPS tracking capabilities which ensure that the closest unit is dispatched to an incident.
The fire engine serves several purposes to the fire company. First, it is their form of transportation around town on errands and to any emergency. Secondly, the fire engine is much like a businessperson's office or a plumber's service truck. Everything the firefighter needs to do their job is carried on that fire engine and the firefighters never know when they might need equipment off of the fire engine for an emergency medical call, a rescue, or a fire. For this reason, the engine company must have all of their tools with them at all times and those tools are carried on the fire engine.
Attempts to Cut Costs
Some fire departments have tried assigning firefighters to pickup trucks or SUVs for medical responses to cut costs, and found themselves on a medical call without their fire engine when a fire call came in. These departments found they were losing valuable time driving back to the fire station to get the fire engine to complete their fire response. In the meantime, the fire grows and crews are unable to make an aggressive interior attack or rescue by the time they arrive resulting in additional property loss and perhaps even life loss. An experiment in saving money like this one usually comes at the expense of someone's property, and perhaps even a life. It's not worth it.