NFPA 70E, in article 130.3(A)(2), allows one to use 1.5 cal/cm^2 as the basis for calculating the AFPB if a) the voltage is greater than 600 V, and b) the clearing time is equal or less than 0.1 sec. If the clearing time is more than 0.1 sec, then 1.2 cal/cm^2 is to be used for calculating the AFPB.

Now, I haven't seen much people use the 1.5 cal/cm^2 for calculating the AFPB.
Is it not used because it's not very known?
Is it not used because article 130.7(C)(5) says that FR PPE is to be worn "wherever there is possible exposure to an electric arc flash above the threshold incident-energy level for a second-degree burn [5 J/cm^2 (1.2 cal/cm^2)]", so per 70E one must wear PPE even outside the AFPB in those conditions?
Is it not used because it increases the hazard outside the AFPB?

What's your opinion on this?

I would guess that it is because:

1) This is a change from the earlier edition of 70E and not everyone is aware of the change.

2) People tend to be conservative with respect to liability/safety.

3) It's one more variable to consider and the whole process is already pretty cumbersome.