Another reason is that all incidents, even cases that turned out to be unfounded are contained in these files. Why would Zalkin need all the US file anyway? because the judge said so?
I have yet to see a case as severe, or similar to the US olympic gymnastic coach, or the Canadian ski coach that had relations with a twelve year old, and got a 15 year old pregnant, among others, show up on the Watch Tower list. By it's nature the religion keeps a lid on things, even on the personal level.
One can not just "release a list" with so many variables in it.