The benefit of commercial space activity is that it harnesses the power of the free market. Free market competition drives a year over year improvement in goods and services through innovation. The ingenuity of entrepreneurs delivers new products and services to consumers for lower and lower prices.
The commercialization of space will occur first in the regions of space closest to Earth spanning the Earth-Moon system called cislunar space. For convenience, I include Near Earth Objects (NEOs) in my definition. The reason for this is that the consumers necessary to drive a free market economy all live on Earth. Hence goods and services derived from space must deliver benefits to consumers on Earth. The real breakthrough will come when the infinite resources of space can be made available for the benefits of humans. This will release humankind from the constraints of finite earth-bound resources and provide the ultimate solution for long range problems like climate change.