The unit of government that adopts the NEC is free to make any changes that it wants to. Many areas have their own local rules that modify the NEC. Look at the inside back cover of the NEC under "adoption by reference". It says, "Any deletions, additions, and changes desired by the adopting agency must be noted separately".
As far as the AFCIs are concerned, I think that they have been promoted as being able to prevent far more fires than they actually will. If you look at the stats in the '98 ROP and ROC used to support the AFCI requirement, you will find that if all bedroom circuits in both new and existing dwelling units had AFCI protection, they would be expected to prevent about 800 fires per year in the US.
Don
