They are a business response to a market demand. SpaceHab, one of the few truly commercial companies to operate under the old paradigm, has signed agreements to build and launch commercial space-station modules that are part of its own business plan for generating entertainment content from space, not a response to a government contract. Another company is developing a space tug that will allow satellites to be serviced in orbit, greatly reducing the risk and operating expenses for satellite companies. Finally, commercial space station is now in operation, run by a private company, MirCorp, not a government. This space station will offer its services based on a company's business plan and ability to pay, not based on political decisions.
Demand drives free markets and industrial expansion.
Several companies are negotiating to use the commercial space station now in orbit for everything from micro-gravity experiments to develop new products, to a base for repairing satellites on orbit, to generating entertainment content. With these first companies benefiting from space as a resource, other companies will demand access. As demand increases for the station's services, more people will be needed in orbit, which will lead to the building of more habitat and the need for more people to be working in orbit. The habitat itself will need to be maintained, and because the people living there are all involved in revenue-producing activities, the crews that constructed the habitat will need to stay. These people living in orbit will need their own services, and soon you will have a thriving economic community.