Limited access can actually be a good thing
Interfaces are complicated. People who work with them frequently get used to them and probably don't notice it any more. This comes up enough with computers, but what about other items? How about home electronics where the computer inside isn't the focus? Imagine the potential complexity of a home entertainment system, for instance.
Maybe you're in this situation. You've put together your own custom mix of items which provides TV shows and movies on demand. Maybe there's a cable hookup, or a satellite provider. There might be a recorder or two adding to the mix of things which are waiting to be played.
It's not much of a stretch to imagine the owner eventually getting used to this system. This is both a matter of familiarity from being around it often and the general need to understand the stuff you paid for.
But... what about guests? They're valid users, too. They didn't build your system and have no idea what went into it. They also haven't been using it for years. Some of the elements might be familiar, but can you really rely on that? Maybe some of your guests know enough about certain systems to know that you might have a significant investment in how it's configured or what programs are currently stored. Will they be able to amuse themselves without worrying about "hurting something"?
Imagine a Tivo, for instance. You might have a whole bunch of season passes and suggestions just waiting to be played. You want your visitors to be able to play through that content on their own, but maybe you're worried about them deleting stuff without realizing it. Or, maybe they are poking around and manage to cancel a recording.
Chances are, they aren't trying to make life miserable for you. They just wanted to watch some TV on an unfamiliar setup and made a misstep. It seems like there should be something which can be done about this. Guests should be able to enjoy the setup without worrying about hurting anything.
Cars already have a system like this. A "valet key" might allow the car to be driven, but it won't remember changes to the seat position, for instance. It might be set to keep them out of the trunk or other non-essential areas of the car.
Why doesn't this exist for home entertainment systems? Imagine a remote control which is recognized as special and can't be used to change season passes, delete recordings, or otherwise interrupt the usual scheduled tasks which happen regularly. It would also be great if it subtracted all of the menu options which make no sense for a guest.
This would benefit multiple parties. Guests would be able to explore without worrying about hurting anything. The system would not let them do anything that might leave a lasting effect. They'd know this and could relax in the knowledge that they couldn't do anything bad. Hosts would also be able to relax and not have to keep an eye on things.
Of course, guests aren't the only interesting use case for something like this. Why not a similarly limited remote control for younger kids? Let them watch their cartoons or other favorites over and over with no danger of them making a mistake and deleting something precious. I hate to think of the tears which might follow a bad button press, especially one which might be avoidable.
In theory, all of this should already be possible. If these entertainment systems were constructed as proper layers with their own responsibilities and strong, well-defined interfaces, then it should be a "simple matter of programming" to make another frontend with limited capabilities. Of course, in practice, I'm sure it'll seem practically impossible to some developers and on some types of A/V hardware.
It's not hard to make a nerd-friendly system. The question is: can you create one that inspires confidence in a young one or a guest who just wants to watch TV and doesn't want to worry about making mistakes?
Not everyone wants to be root on the TV.