The concept goes like this:
We want to solve problems today, such as jomelessness or poverty of street crime. However, doing so is a long and complicated process, because we just don't have the resources to do it. The near solar system has resources in abundance. The energy released from the sun in a day is more than humanity has ever produced, the metal in one or two of the medium sized asteroids in the asteroid belt is more than in every skyscraper in the country. There are resources in abundance, and if we can utilize even a fraction of them, we'll find ourselves in a better postion to deal with issues at home. This discounts all the technology improvements we'll see as well. To this end we should put a massive investment into space travel and exploitation sciences.