[Socialists] Why do people seem more willing to emigrate from left ruled countries to countries with more free markets than viceversa?

The countries which have experienced left regimes, such as China, Cuba, Syria tend to have big diasporas worldwide, while countries which tend to have pro-market tendencies don’t tend to do so.

Why do you believe that happens? If socialism means well-being, then why people seem to emigrate away from it?