Because a very significant majority of the time, the guy in India is not worth what he is paid.
On the contrary. The products of our public mis-educaton system cannot shine the shoes of many Indians in IT. I've worked at many IT shops in the midwest with significant Indian immigrant and outsourcing components.
In general, they are more capable of dealing with facts and logic whereas young American workers have only learned how to "feel" about a topic. Also Indians have a better work ethic than many of us Americans (I say as I chat on the internet at work).