“citizens”, “customers” and “politicians” are three different groups. The government might want to use the airline as tax revenue, artificially increasing prices on customers to support non-customers.

Or the government may want to give their airline unfair advantages, which would decrease real competition and create a brittle industry. Or the government might want to strangle their own company, in order to declare that it is “bad and dumb” in order to manufacture popular support to privatize the public company.