True but as far as we can tell it was usually (if not entirely exclusively) done through the same social networks that existed locally [unless you were leaving to murder/rape/rob people]. Unless they really, really had to you only moved to another city/location because you had a cousin, uncle etc. or someone else there you had some ties with. Outside of organizations like the church or the army (and even then) a complete outsider was at an extreme disadvantage (relative to today).