A decentralized market economy requires the establishment of property rights. The existence of property rights allows voluntary market transactions to work well.
Government establishes and protects property rights more efficienfiy than private firms.
Private protection can result in the free rider problem. A free rider is someone who uses the goods or services provided by others without paying for them. The free rider problem means that too little of the good is provided. It is generally cheaper to have a single agency provide property rights. The protection of property rights probably requires coercion.