Was the much smaller Bae-146/RJ-70 Avro (60-75 passengers)designed with four engines because of an RAF requirement to transport Her Majesty the Queen over water, and having two engines created too much concern?
If this was the case, then lesser mortals are deemed an acceptable risk for the majority of newer aircraft which all, except for the MD-11 and A-340, Boeing 747, just plain economics?
The US FAA would call it cost/benefit ratio during the regulation, certification process.
