Re: I ran a payrolll system
Just a guess here - these DVRs are for shops who DON'T have a DVR specialist on staff, so the passwords are for the hired-in CCTV contractors (who, in my experience, generally only have the slightest of ideas about how networks work to start with). So instead of rolling a truck for every call, the CCTV guys can remote-in and check on things or fix/change things in the DVR. Fairy-magic it is.
It's not like Rosie the Florist can figure out how to change the admin password in her DVR every time she needs Joe Bob's Fire Alarm and CCTV Shop to login to her DVR and update the camera names.
But like I said, that's just my guess. I could well be wrong. I'm not saying you're wrong, just that these may be aimed at a lower-tech target audience.