It's human nature to suppose that the status quo will continue indefinitely. This is true regardless of what the status quo is. For example, during WWII it will have quickly seemed that the state of war had lasted forever and would last forever more, even though logically it isn't true. My own basic drive towards preparedness is the observation that nothing lasts forever.

A second factor is that if the powers that be try to get us to prepare for disaster, it will be seen as an admission that they can't do their job of averting disaster. It's politically very difficult for them.