Public Corporations are established mainly to provide services at subsidized rates.
Looking into the definition of Public Corporations, it should be realized that they are business organizations which are set up by an Act of Parliament or Decree to provide certain social welfare services for the public which if provided by private entrepreneurs will be very costly.
One of the major reasons for setting up Public corporations is to provide essential goods and services at cheaper rates for the people. Another is to protect the consumers from Shylock traders and manufacturers, provision of employment opportunities etc.