If you think of it however as not needing to be rational, but more or from an evolutionary perspective ‘folks in the past who had similar types of fears and discomfort might have survived prior insane disasters that no one else expected to ever occur’ it might make more sense.

It doesn’t have to be rational. It doesn’t even have to help them survive or be successful most of the time. If it works even a little better and they survive when everyone else died because of their insane paranoia, those genes will propagate.

Most of us prepare for short-term disruptions that are far more likely than hordes of undead roaming the streets. If widespread societal collapse should actually happen, then having a strong local community, and knowing how to co-operate and communicate with one's neighbours is far more important than having enough canned tuna to last to Ragnarok and back. That being said, having survival skills and basic supplies can come in handy in a wide range of situations.

Personally, I'm preparing for more basic things like long power outages, extreme weather and supply chain disruptions. Sure, we got food, fuel and supplies for a few months at home, and it's been very handy during the pandemic, while being snowed in for a week a few winters ago, and when being without power for two days last summer -- I could keep working like any other day, and didn't lose any income.

Yes, that includes some cash. It's been handy a few times when the card terminals at the store wasn't working. Storing large piles of it seems an unnecessary risk, though.