The last thing you want is someone forgetting their password to their tactical system while out at sea and having to sail back into port to get the vendor to reset it for you.
And really, the first case is no worse than the old days with manual controls that just anybody could walk up and fiddle with.
In that case, you could trust physical security to some extent; someone really not intended to be in contact with the device could be prevented from doing so by some dude with a big gun. Now, those devices are networked, so someone could figure out an access method and use it on all the devices in the field at will.