Probably because if the system glitches out and they can't into the room anymore (even with maintenance keys) then they wouldn't ever be able to fix it?
Well, you can always drill the lock cylinder out, but that's a destructive process. It is possible to do this sort of thing in the right way, they just didn't.
Once the batteries go out (they're not powered on guest room doors), the lock won't open to keycards anymore. The batteries, though, are on the front of the door just below the handle (see the panel at the bottom, in the story photo) and can be replaced from the outside. Otherwise, it's possible to use the portable programmer's open function to open the lock, if the batteries in the PP are full enough; that's really iffy and has a tendency to not work, though.
And you can still have a DC power port on the outside in case of a powered-down door, just no programming access.
Why have they not done it that way???