Usually they come here to earn an acredited education. A BS degree in india is basically equal to an AAS 1/2 degree in the USA and a lot of their universities are 3 yrs instead of 4. Some students like the idea of capitalism and stay while others are here to learn, earn a good income and ship it back home and inect those funds into their own ecomomy. There is also a percentage of overseas companies who intentionally plant these 'seeds' in organizatons so they can develop business opportunities for their offshore counterparts. They then leave, taking their money and knowlege with them.
The only way to fix this is to have more Americans get educated in the field such as software engineering so there's not a labor shortage. Dispite the high rate of unemployment these skills are very much in need. Unfortunately kids these days aren't interested in SW eng. and are allured to investmend banking for instance or expect to be mangers right out of college, lol
Anyway, were a bit off-topic now.