Having flown military jets during training, military helicopters and light fixed wing and carried out RIABs on all of them, I see RIAB as a punchy and extroverted way of joining the circuit in an expeditious way. The origins of the manoeuvre have already been mentioned.
There are risks in the manoeuvre, tragically demonstrated by the mid-air already mentioned. However, aircraft do collide in the circuit in other circumstances that all pilots would consider more "normal", irrespective of their experience and training. For example, two gliders collided on finals whilst landing at Camphill about 4 years ago.
The common thread is insufficient lookout, with perhaps a lack of awareness by one or both pilots. As far as I was taught, it is the responsibility of the pilot joining the circuit to fit in with other traffic already in the pattern and cause no inconvenience or danger, just like road traffic joining a roundabout, or driving / flying in general.
IMHO the North Weald mid air was the fault of the Yak pilot. He failed to safely carry out a manoeuvre that was beyond the experience of the other pilot.
BTW, military airfields always have a Flying Order outlining the procedure for a RIAB, giving details of the position of "Initials", radio calls etc etc.