Why are there actually relatively few markets in which there is perfect competition

Barriers keep markets from entering the market freely.

Government interference often creates problems that affect the market negatively. Many countries even have laws that protect big companies, making the country go through a corporatism sort of state that involves a lot of lobbyists and the use of legal devices to protect the corporations. Many times, this protection appears in the form of barriers for new competitors that are often disguised as laws to protect the consumer, but in the end, only exist to eradicate small companies.