This prevents predatory pricing against the people. It also allows the govt to fund itself without taxes. Assets like airports are a good example of this. Profits can be made, without ripping people off with monopoly power.
With the example of airports - gate fees, security fees, passenger fees become added pass-through costs to the end consumer. These ‘economic rents’ are unjust and add to inflation problems.
The private sector can do better in most fields, however natural monopolies are not an area where this occurs.