The revolutionary breakthrough will come with rockets that are fully and rapidly reusable. We will never conquer Mars unless we do that. It'll be too expensive. The American colonies would never have been pioneered if the ships that crossed the ocean hadn't been reusable.
Elon MuskIt's not as though we can keep burning coal in our power plants. Coal is a finite resource, too. We must find alternatives, and it's a better idea to find alternatives sooner then wait until we run out of coal, and in the meantime, put God knows how many trillions of tons of CO2 that used to be buried underground into the atmosphere.
Elon Musk