Doomsday:
1 - The last day of the world's existence.
No point in preparing for that (physically).
But, there are "limited" doomsday scenarios, like man made ones. And, anything man made can be defeated. Preparation can improve your, or your family's "odds". And, the worst threat from a man-made doomsday, is still from other men trying to survive at any cost.
If someone learns you have a 10 year supply of food, that they didn't prepare for, do you change that to a 5 year supply, or a 1 day supply for the entire city? Or, simply die cause you're in the way, (and have no authority to have it, or keep it).