The boring answer: criminal investigative files generally aren’t released, so they’re compiled in a way that mingles information about victims with information about suspects and witnesses and others potentially involved in criminal activity, intentionally or unwittingly, directly or tangentially.

If you want to export a list of all names in the files, you’ll want to filter out victims for sure, and probably mere witnesses. You definitely don’t want to out informants and make them vulnerable to retaliation.

So most law enforcement agencies simply will keep everything secret. The idea of releasing names from the file was unusual, and it’s not surprising that Trump’s own people refused to follow through, especially when it’s highly likely that Trump was in that list of names.