In most cases, files on a storage unit are not needed to be secure. Most people might believe that files on their computer are safe, especially if they enter a password to log in.
In networking, a network drive, a storage drive on another system, should have permissions set that only the specific user (and administrators) can access the data. Local storage devices, those connected directly to the local computer, may not have such permissions. Another user can log into a computer and have access to nearly all the files on the local storage devices.