[chu4n]

Because of normalcy bias: https://en.wikipedia.org/wiki/Normalcy_bias

"Normalcy bias can cause people to drastically underestimate the effects of the disaster. Therefore, people think that they will be safe even though information from the radio, television, or neighbors gives them reasons to believe there is a risk."

People just don't want to believe a disaster is about to happen. They will grasp at straws to explain why everything is going to be fine.

That's usually not a problem because disasters are rare, but it will catch us under-prepped when an actual disaster happens.