Check out the pictures here: https://deskthority.net/viewtopic.php?t=17354
The RESET key is so well-hidden it's not even visible in the first picture. In the second picture, you can see the notch along the back of the keyboard near the numeric keypad. In the third picture, with the cover removed, you can how the key extends backward at a perpendicular angle.
You're never going to hit that thing by mistake. You might not even realize it exists until someone points it out to you.
Remember the original computer didn't have a disk yet. The only storage was a cassette tape operating at 6000 baud. You didn't hack on it by editting a text file and then compiling it from storage, you programmed in-memory (either in BASIC or by hand-assembling instructions at the monitor). Then you tried it, and if it worked you started worrying about how to get that pickled to storage in a recoverable way.
It was a different world, and "reset" was absolutely a critical feature.
But yeah, fast forward a few years and the median user was "running" software and not writing it, and we all forgot about why it was there.
But one nice feature was that if you were simply programming in BASIC and immediately typed OLD after hitting "Break", you had a chance of recovering your program if you weren't unlucky.
And the other feature which this comment reminded me of - at least some models of the BBC Micro had a hardware lock on the "Break" key, so with a small screwdriver you could turn a little piece of plastic to completely prevent the key being pressed!