The government might become involved when there are human rights issues at stake, when there are issues with revenues at the federal level, and when competition is threatened by the rise of companies that are monopolizing certain areas. Human rights issues might make it less possible for certain classes of people to be a part of the economy, lack of revenue collection (for things like taxes) might require federal intervention to instigate changes in tax codes, and monopolies might threaten the ability for some companies to get a foothold in a certain industry. So the correct answer is TO PROVIDE PUBLIC GOODS AND SERVICES TO ITS CITIZENS.
