What? I don't even know how to begin to respond to something so absurd.
First off, if they don't want to be citizens, they certainly don't have to be. And as far as reaping the economic benefits--of course! That's why almost anyone immigrates. You could make that same statement for most of the immigrants to the United State throughout history.
Hey, if they want to come here and speak Spanish and eat their food, whatever. I don't care. Like I said before: larger market, more opportunity for division of labor. Welcome.