People seek to restrain the free market out of concern for equity. Markets are a natural outgrowth of human civilization.
People trade in order to satisfy their desires with less exertion.
It follows that markets are free unless something is done to make them not free. Some things that restrict the freedom of markets are subsidies, monopolies, protection, favortism or corruption on the part of the government, imperialism, or crime. To keep this from happening, or at least from happening to uncomfortably many people, governments seek to impose fairness on markets by redistributive tax and welfare policies. These, of course, often serve merely as invitations to corruption. On the other hand, Karl Marx said that a free market inherently leads to the savage exploitation of labor, and therefore is only a transitional stage in the historical march toward communism.