Illegal Immigrants Flow Home from U.S.

Today's Miami Herald front page story is about the economy and how illegal aliens are heading home.  It is Sunday and I don't have much to say today except this:

Immigrant labor, legal or illegal, is like any other commodity and affected by supply and demand.  The unskilled workers who are the bedrock of much of a healthy U.S. economy by filling the jobs Americans don't want cross the border illegally to make a buck because they have no way to legally work here despite the demand for their services; when their labor is no longer needed, they go home.

Instead of demonizing these workers, why not establish visa categories which permit them to work legally when the economy has recovered and our hospitality, manufacturing, and construction sectors again need them?  If we can have visas for foreign "professional workers" despite the loud rumbles of the health-care, IT, and various other U.S. labor lobbies…what is the rationale for not permitting similar temporary visas for those jobs which are so rarely filled by U.S. workers that labor lobbies for them simply do not exist?