Because of the innate desire of humans to explore beyond our home planet. Oil, coal and gas provide the three essential elements to get us to even greater reservoirs of hydrocarbons, our solar system's gas giants. Hydrogen and oxygen sustains lives, of course, and carbon will be used for building materials. But first, we have a lot of experimenting to do and issues to resolve. Graphene filters are needed to provide clean drinking water for the world's people, plants and animals, a money maker if there ever was one. The world's oil and gas companies understand economies of scale, political processes and how deep investment can generate extraordinary returns, so they'll quickly be on board with carbon nanotubes braided into tethers moving energy generation to low earth orbit, away from the attenuation of our atmosphere. All they need is a process, and the development of graphene and carbon nanotube primary manufacturing standards seem to be developing quickly. That's the basics for carbon, but what about O and H? Oxygen and hydrogen dumped into the atmosphere as waste would be stupid, and maybe poisonous. We need both in copious quantities off planet to continue exploring. Us, not our robots and unmanned spacecraft. Tools always help during exploration but have proven crappy at insight. I want to go and do, and as the media has shown, there are plenty of people willing to pay to watch me go and do. But I have to breathe, eat and drink if I'm going to do it away from earth. In my diamond greenhouse spacecraft with full-ship surround sound.
Challenge Timothy W Loomis to a bet on this prediction!