OK, we see what these devices do and how they work. Still, it would be useful if they could not be disabled from the cockpit. Pulling a breaker does not have to shut the black boxes off. They can be designed to continue on battery power, and turn themselves off when a the end of a flight is detected. Airplay mentions a couple of ways that can be done, I am sure we could find dozens more.
Similarly, transponders can switch automatically in case of failures.
While these are not essential for safety of flight, they are useful for finding out what went wrong (black boxes) or what is about to go wrong (transponders). So what's wrong with this idea?
"In God we trust, everyone else bring data"