Rationale
The primary purpose of a bug-out bag is to allow one to evacuate quickly if a disaster should strike. It is therefore prudent to gather all of the materials and supplies that might be required to do this into a single place, such as a bag or a few storage containers. The recommendation that a bug-out bag contain enough supplies for seventy-two hours arises from advice from organizations responsible for disaster relief and management that it may take them up to seventy-two hours to reach people affected by a disaster and offer help. The bag's contents may vary according to the region of the user, as someone evacuating from the path of a hurricane may have different supplies from someone one who lives in an area prone to tornadoes or wildfires.
In addition to allowing one to survive a disaster evacuation, a bug-out bag may also be utilized when sheltering in place as a response to emergencies such as house fires, blackouts, tornadoes, and other severe natural disasters.
Read more about this topic: Bug-out Bag