Today, market-based economies are being used by the great majority of the countries of the world. Essentially all of the major economies of the world are based on the market. Even China, which has a great deal of government control of its economy, has an economy that is significantly based on market principles. There are at least two reasons for this.
First, market economies provide the greatest amount of freedom. People typically prefer not to be told what to do with their property. Market economies give them the freedom to do what they want economically speaking.
Second, and more importantly, market economies give consumers more goods and services of higher qualities and at lower prices. Command economies typically end up producing very poor goods and services and not enough of them. We can see this, for example, in the degree of poverty being experienced by Cuba or North Korea. In market economies, the profit motive drives producers to make goods that are as good as possible and as cheap as possible. Producers do so in hopes of making money.
Countries are typically opting for market economies because of these two benefits.