I would guess many of them want to contribute to solving big global challenges rather than simply focusing on a single country?
Not saying that working in a country with no regulatory or physical infrastructure is easy, but buying a bunch of mosquito nets is much cheaper with very few unintended consequences compared to doing something like OP suggested. For instance, wouldn't a revived/subsidized CC put a lot of current companies/workers out of business? How would that opportunity effect a high schoolers decision making? Is this something that goes on forever, it sounds like we would be training more people to do a job then would be needed if this program stopped. etc, etc, etc.