A potentially legitimate reason is referenced at the end of the article you linked: that publicly releasing the files before Ghislaine Maxwell's trial is complete could provide Maxwell's lawyers the opportunity to argue that it prejudiced the jury. It would be giving them free ammunition for no particularly good reason.

A less legitimate potential reason might be that Trump and/or others are indicted by the files. If I'm not mistaken, they relate to Virginia Roberts/Giuffre's lawsuit against Epstien. She was working at Trump's Mar-a-Lago Resort when Epstien recruited her, and it's possible that there's more to that story that hasn't been made public.