Comment by mdpopescu

It's a matter of degree. There is no 100% free market - your transactions are influenced by a lot of factors, from the taxes in Nicaragua to your physical location. Government intervention is one of those limiting factors; mobsters demanding protection money from a shop owner is another.

We (libertarians) prefer the markets to be as free as possible (with an ideal of 100% free) because we've seen a direct relationship between market freedom and economic prosperity (utilitarians) and / or because we find it more moral than the alternative.