Immigration is allowed (both legaly and illegaly) because payment for some activities isn't a honest wage for an honest job. Why? Because the game is rigged. *
Not everybody can apply for venture capital investment. Being white helps. Being male helps. Having the correct background helps. Having a good idea helps. Making a good pitch helps a lot. Why? Because the game is rigged.
Those two generalizations should be enough.
*Why do border exists, again? To keep away the slave labor reserve until it is needed. Why can people from any country trade their labor? Because the game is rigged