How so? Anybody who has a student visa had to prove that she or he has strong ties to the home country and no intent to remain in the Untied States, and that she or he only needs to get education in the US to come back and apply it for the home country's benefit.

If these people have not defrauded the US then they would not know what to do with a work visa as they'd be hurrying back home as soon as they received their diploma, pulled by those strong ties and the desire to finally put the education to use at home.