Earlier quoted context omitted.
AFCI's are of dubious effectiveness at their purpose (preventing fires). They're kinda snake oil because each manufacturer won't tell you under what exact conditions they'll trip. Somehow the law in the USA now requires them on every circuit, although they aren't used at all in Europe (which has a higher voltage yet far fewer electrical deaths).
I'm not sure where you are getting this. According to the CPSC, who analyzed some 10s of thousands of fires, something like 50% of them were caused by wire arcing that could be prevented with AFCI breakers. This is the exact reason why the NFPA is moving the NEC towards eventually requiring AFCI on every circuit in the house.
Do AFCIs actually do their prescribed function effectively?