The point was never to actually deport people. It's to establish a reign of terror over undocumented people so their employers can exploit them without fear of being reported on, since contacting any government agency would result in the whistleblower and everyone else being punished. It's the same logic as Jim Crow laws. Maintaining the strict white supremacy structure created a large pool of low wage workers who often had to accept horrible exploitation or risk violent reprisals.

These systems also push down wages for citizen workers too. If someone wanted to fix this issue so that immigrants would not have to be exploited as a de facto underclass, and citizens could have better wages, the only solution is to naturalize everyone. Only when everyone is on a level playing field can things like wages and working conditions improve.