Comment by XorNot

The JFK documents were classified to protect methods, and are still classified to protect people. People who are still alive, were tangentially involved (e.g. clerical staff or random bystanders who might've been interviewed but reported nothing of note).

It's why releasing more documents never reveals anything: it's stuff that wasn't worth trying to declassify because it's irrelevant, but it might contain a bunch of random names of people who are still alive and did things like sign for lunch that day.