I would need to access the NFPA Codes to be certain but I suspect the ranchers and others you obsreve are not in compliance. Flammable liquid in commercial settings require storage cabinets and grounding for dispensing. There is a limit to the number of cabinets allowed in one fire division (3) if I remember correctly, separated by something like 25 feet.
Anyway free standing barrels in the open are not in compliance. In the past nfpa 30 allowed wooden cabinets constructed of 1″ thick boards. Flammable liquid storage rooms can be constucted as well. The room required positive ventilation, vapor proof electrical equipment, grounding for the barrels.
I found NFPA 30 in a pdf but the link is hard to post from my tablet.