Particularly a while ago it was nearly impossible to utilize the program because it was a bureaucratic and underfunded mess. So the number who qualified was effectively zero.
Now it's marginally less terrible and actually forgiving some people's loans.
Specifically, the previous Dept of Ed administration torpedoed the program. When the first class of PSLF candidates hit the 10 yr mark in 2017, 99% were rejected [0].
Now it's marginally less terrible and actually forgiving some people's loans.