It seems the problem is bad corporate file sharing policies that are incorrectly validated as successful because the employees are using workarounds rather than pointing out its inadequacies.
One of many depressingly common pathologies in large organizations. The best way to ensure your infrastructure won't break is to ensure it's not used; whether or not that means people can do their job is a concern for a different department.
Welcome to the real world! :)
I have seen this kind of situation, too. It sucks, but if you play by the corporate rulebook and lobby for better rules, you will be either worn out or retired by the time those rules get updated.
* A ban on mail attachments of certain types (excel, zip files...) * mailbox limits from the 1990’s (100MB or so) * a ban on Dropbox, Gdrive or any other file sharing service * No public facing sftp or similar * A web site so mired in red tape that it takes 6 months and a dozen approvals to get anything uploaded.
Often the USB drive or something similar is the only way for employees to actually do their jobs.