That's only one variable in the equation. Many of the employers are... shall we say not engaged in wholely upright businesses. The areas between the ports of entry have to be sealed tight, yet those who want to follow the rules need a means to come in legally.
That's a big problem in NY now, lots of businesses doing under the table work using illegals. Btw I agree, we need better patrolling of the borders as well. And cut the benefits out too.