A commercial intent will be driving the interest to explore and exploit space resources in the 21st century, but what is most focused upon  now is services not building infrastructure. Those services  are furnishing things to government space programs, with some hope that other companies might develop orbital service needs for such things as tourism and satellite maintenance. Yet what might really be needed most over this second era of spaceflight is building a space infrastructure.

When infrastructure is built, it creates new capacities in new locations. These new capacities are in transportation, communication, and logistics. This creates new opportunities to achieve new endeavors never done in that location before. And new endeavors can create both new motivations for more activity and yet more infrastructure. The whole process is a self promoting open ended cycle if sustained, but there is always that initial cost and necessity.

Historical equivalents on Earth were mostly driven by new settlement of lands and military expeditions, but some mercantile activity also drove new infrastructure needs. A good example is the Roman building of roads across Europe. The areas in central and western Europe the Romans built roads into allowed expansion of the Roman civilization into those areas. This was primary a military conquest activity, but trade and commerce soon were using the roads. There was an ease of travel and transport that was created by the road network.

The American westward expansion was similar. Wagon trains and explorers could map out the North American continent and contact the various indigenous tribes, but once the transcontinental railroad was built large amounts of peoples and goods could be moved from the east coast all the way to the west coast. The United States would not have industrialized a continent without that initial building of the railroad.

These are not complete analogous because those regions were already inhabited by native peoples, who created a situation that any expansion would be a matter of military conquest and cultural assimilation. Outer space is a place where no human life can exist without technology. The unique opportunity is that while learning how human life can sustain long term spatial habitation against the dangerous of microgravity and radiation, the infrastructure for that long term habitation can be developed as part of the testing and learning.

All of this means that planned infrastructure development for humans initial space habitation development is essential. The more we build for the long term and with increase capacity, the more that can be built.