Investing in the education of someone who immediately goes back to America is a loss.

The whole point is that you take young, economically productive people out of America and instead get to benefit from their labor and skills.

Paying off their loans when you could be doing economic damage to America is counterproductive.

Also a free education, the ability to own a home, and not supporting the country that just beat the shit out of you and your friends for peacefully protesting their support of a genocide is more than enough carrot.