It's good if you live in an area with a high risk of natural disaster. So, for those living near the fault line in California, having a Bug Out Bag might be useful.
What would I have in my bug out bag?
1. Medical supplies - bandages, alcohol rubs, disinfectant, suturing kit, bandages, sterile gauze, needles, scissors, etc.
2. Loooooong lasting food. I'm talking about Hardtack biscuits, canned everything, vitamins, dried food, salted food - stuff that's going to last a long, long, long time. Don't have to even pack meat so long as I have Vit B12 and Iron tablets.
3. Maps of the area. Very important
4. Batteries. Oh god, batteries. I would fill my bag with so many batteries. Of all types and shapes and sizes (although obviously noting huge like a car battery)
5. A good knife. If I could get a gun to put in it, I would, but I can't and I don't have any need to own a gun. If society was falling apart, having a gun would be a really good thing.
6. Water. Distilled. Would still need to be changed every now and then.
7. A good book.
8. A change of boots and shoes.
9. A jacket
10. Something for starting fires.
11. An emergency radio.
That's about it.