Looking at the top posts on /r/prepping right now, you can find these two images:
I used to think that people who are stockpiling food, water, and guns out of fear of are acting irrationally. But then I realized maybe they just have different utility functions than me.
I think preppers have a satisficing utility function. As an exaggerated example, imagine a utility function where you got 1 utility each day from having enough food and water, and 0 utility from not having enough food or water. If you had that utility function, you really should start stockpiling food and water immediately!
Arguments about prepping are often have the general form of a prepper saying "it improves the worst-case outcomes in lots of scenarios" and a non-prepper saying "but it doesn't maximize expected value!". If you accept that the source of the disagreement is preppers having satisficing utility functions, and non-preppers having maximizing utility functions, you can see the futility of that line of argument. Telling someone their utility function is wrong won't get them to change their utility function.
Once I started thinking about preppers as satisficers, I realized why they are so worried about civilizational collapse. If you feel reliant on other people to provide you with the resources you need to meet your satisficing threshold, then reducing that reliance would be a high priority.
While I have you here and we are talking about prepping, I'm going to try to convince you to store a little water in your house. Water is one of the largest (by volume) necessary inputs to human life. If the water main burst in your house, it would be highly inconvenient and would require moving. If a natural disaster took out running water in your neighborhood or city, it might be a humanitarian crisis. Buying some large jugs of water and stashing them under your bed is a very cheap, low-cost intervention that has a decent chance of greatly improving your life if you lose access to running water.
I doubt it's a difference in utility function (the value placed on a given state of the world), but in the distribution of predicted event. If you're worried about a sudden event that disrupts everything for a few weeks to months, then surviving that with stored food and defense is what you plan for. If you're worried about a complete collapse to pre-industrial capacity, then you think about seeds and skills to make rebuilding slightly faster (even if not in your lifetime, perhaps your grandkids).
What the second group forgets is that even if it's a long-term collapse, there's still 1-10 years of short-term violence and starving people trying to eat your seed stock. You may not need lots of guns, but you need lots of people you trust who have guns.
Having lots of potable water around is definitely a good start. That's one of the reasons I argue against tankless water heaters - having 40-60 gallons of stored water is rarely a bad thing. If you don't have a few weeks' worth of food and medicine that doesn't require electricity to eat, that's also valuable in a very wide range of scenarios.