Countries are monopolies
Monopoly: the exclusive possession or control of the supply of or trade in a commodity or service.
Until recently you were trapped in the country you were born. However, things have changed. Now it is much easier to change countries, move assets, and even secede. Society is becoming more fluid. Borders too. Hopefully, the states will soon realize that coercion does not make things better. But right now, only few citizens realize and are able to stand up and leave.
To further develop the idea you may want to check Citizenship beyond the state from John Hoffman