Because it's a transcation and there are two parties to the transaction. And for these transaction to occur in a repeated fashion neither side should feel they are being taken advantage of.

I don't think anyone feels taken advantage of. I think most people involved in academia value the complexities and jagged edges that come with an international student body. And the outcome - the preeminent education system in the world that keeps the US at the cutting edge of science and technology and has for nearly a hundred years - is indisputable.