Maybe it's the same few who are deported time after time.
If I were sneaking in, I would bring my fat friend Pedro. I wouldn't have to outrun the border patrol - I would just have to outrun Pedro. Sorry, Pedro, but it looks like you were caught again.
Years ago when hiring standards were even less stringent my dad was working for the phone company at a construction sight. One day he got there and there was no work being done. They were shut down because INS had caught them and deported them.
He asked the owner if it was a problem and the guy said it would cause a delay of a couple of days, but the workers would be back in town before the officers that escorted them to the border.
2 days later the workers were back and the officers were still at the border.