Survival Someday the Earth will become uninhabitable. Before then humanity must move off planet or become extinct. One potential near term disaster is collision with a large comet or asteroid. Such a collision could kill billions of people. Large collisions have occured in the past, destroying many species.
Future collisions are inevitable, although unpredictable.
If there were a major collision today, not only would billions of people die, but recovery would be difficult since everyone would be affected. If major space settlements are built before the next collision, the unaffected space settlements can provide aid, much as we offer help when disaster strikes another part of the world. Even given ample funds the first settlement will take decades to construct. No one is building a space settlement today, and there are no immediate prospects for large amounts of money, so the first settlement will be awhile. If the first settlement is designed to build additional settlements, colonization could proceed quite rapidly.