There are people who haven't come into this country illegally, who are waiting at the end of the line, to get temporary visas.
If you give visas people who have snuck into this country, then you reward their behavior and you hurt the people who are patiently playing by the rules.
That's a form of amnesty and it will only encourage more people to come into this country illegally.
Perry has said that those who get worker visas coming in illegally go to the back of the line (And they get mapped)