So far, only human arrogance and sensationalistic journalism says they are. Personally, I know that earth-like planets and life are rampant throughout the universe. Over 5 billion people are trying to survive on this speck in the cosmos. This figure is predicted to triple by the year 2050. This is inevitable and obvious to some of us because of the depletion of the nutrients in the soils, the ozone layer and the rain forests, and air pollution, population, green house effect, global warming, etc, etc.
Space development is the only logical progression.
We must take advantage of our only limitless resource - space. Our meager space efforts should be doubled and redoubled - regardless of the dollar cost. International cooperation is imperative. The future of the human species is among the stars that created us. Earth is an embryo of creation and we are not yet born to our true purpose.