The answer is simple: the biggest customers for 4WD light trucks are the mining companies and they do NOT want discs brakes on trucks because they wear out too quickly in the abrasive environment.
You can get a disk brake conversion for mining purposes but they are sealed disc brakes in a silicon fluid and V expensive.
I have all the drawings/approval for converting ISUZU NPS to disks (similar conversion for the small Fuso) but require a minimum order of 200 custom made rotors as there is no standard rotor for any vehicle that will fit either directly or with an adapter so its all on hold until one of the big boys (i.e. ATW) gets involved to order rotors.
