And golly gee, ruthless exploitation of immigrants in the finest traditions of the gilded age. Yes its somewhat skilled labor, but skills can be trained. Hand tossing pizza crusts is also a skill, and I could do that inside a week of working part time! I think that they don't WANT to try and deal with Americans who *gasp* need to be trained, provided any sort of benefits, paid minimum wage at worst... At best the good ones get $15-20 an hour! Most get even less than that!
If you've ever watched something like Dirty Jobs, then you'd know that Americans will do some of the most brutal and nasty jobs. The thing is, they get benefits out of their labor and are protected from the worse abuses, and can get assistance when they need it.
I do concur that the US immigration policy needs to be revamped and cut down though, as the current setup is insulting to the people who came through legally.