Humans tend to be driven towards only a few things. At a macro level, these resolve into economic profit, and war. Regardless of how much wealth or how comfortable human lives are today, humans will strive to be better than their neighbor. On the whole, this has been a good trend, driving cheaply available food, medicine, transport, communication, and other activities. The downside of this is that those who cannot afford to purchase these improved goods through economic means have a tendency to take them via raiding, and warfare. The Vikings, for instance, stopped raiding in large part because they had now accumulated enough wealth they could live comfortably with the economic system of their day. And these activities are equally prevalent today, from the Somali pirates to economic competition among nations.
And sooner or later, a nation will decide it cannot compete through economic means. In World War II, this was the Greater East Asia Co-Prosperity Sphere, better known as the Japanese Empire. Japan used military force to acquire to itself resources it was having difficulty attaining. Similarly, the German concept of lebensraum was built around allocating resources to the most deserving of people.
That war was fought just before the advent of nuclear weaponry, indeed, driving its development during the last days of the war. Since that time, no country has felt in such economic peril that they need use a weapon of such indiscriminate power. With luck, no country will. But given that is but a faint hope, sooner or later the third nuclear weapon will be detonated in anger on Earth’s soil. And at that time, it would be far better if humanity did not entirely reside on a single blue-green marble.
Thus humanity must hope that the economic exploitation of space occurs, but also must hope that it occurs at a time far enough in advance of the consequences of the imbalanced economic results that humanity will not be killed by the resultant war. Lest this seem a far-fetched statement, it should be noted that the asteroid Eros contains “more aluminium, gold, silver, zinc and other base and precious metals than have ever been excavated in history or indeed, could ever be excavated from the upper layers of the Earth’s crust.” If a single national government could hold access to a deposit of that size, think on what it could do to the economic markets. Then wonder on the reaction from affected countries.
Yes, space development and settlement matters. But perhaps the consequences aren’t as rosy as humankind would all hope.