Predictions of Doom

Why do predictions of the end of the world always involve only earth? does that mean that we will never extend humanity beyond the reaches of this planet or does it just mean that prophets heve left out the idea that man will allways keep expanding?

ive always wonderd this i think it shouldnt be the end of the world it should be "The end of Man"

and one have any ideas to this?

Guess we humans have a subliminal death wish Thanatos.

if the water surface furthermore rise... the end of humanity - the beginning of the fishes