I got an email about PSLF today. I chose not to pursue this route because they were rejecting well over 90% of applicants. It is one of the reasons I live abroad where I can have decent national health insurance (ambulance = $0). I am happy for the people getting credit for forgiveness but knowing that they were not keeping their end of the bargain was enough to dissuade me from teaching in the US.
Another reason for cancelation is people who chose not to pursue programs that the government did not honor, leading people to pursue different options.