As an individual, you are responsible for yourself, and preparing for every improbable event would not be a good time / life enjoyment trade off.

As a society, we are responsible for not only our society, but we also set the stage for the entire future of the human race. Though an improbable event probably won’t happen tomorrow, we can say with a certain amount of assurance that it will happen in the future.

Therefore we can and should prepare for these events.