Some of those plans charge a fee to get you connected. Doctors can help people find the true PAP's that are direct with the drug companies. Those programs are based on income and are good for those that have no RX coverage or their plan doesn't cover one of their expensive meds or it a high tier drug.
I have directed people to those programs in the past, and they do work/help. I think it's easier for a person to look into if they have Internet access, which several seniors don't have, so I used to refer them to a lady in Texas who has made a career out of doing the the applications for people and charging them a small fee.
A scenario where I might recommend it might be when a person makes too much money to qualify for "extra help" but still has meds that cost a lot. Since the PAP is not run through the government, sometimes the parameters for qualification are a bit more liberal.
I am a huge fan of the Needymeds site for the fact it has more than just medical assistance programs.
They have disease specific resources, free Rx cards (yes, I know they do not work for Part D, but a nice piece for the client to pass to friends / family), low cost / free clinic listings, etc.