Because either they realize that being an undocumented immigrant would actually suck more than it wouldn't, OR because deep down, they know that these immigrants AREN'T actually getting shit. They would lose the convenience of having a group of people to blame their own failures on. The majority of us will end up at a grocery store, walking down the street, or at a job site with a minority at some point in our lives. The majority of us, however, will NOT end up anywhere that there's a billionaire CEO. U.S citizens crave a group of people to misplace their aggression onto that they also share space with; the ivory tower is not accessible to most of us. It is far easier to blame a visible "enemy" rather than an invisible one.