Reddog1 wrote:
Not looking for logic, looking for a why.
WHY.....because DOT (Department Of Transportation) requires it on portable cylinders and has lawful authorization with the means of enforcement
ASME/NFPA ( American Society of Mechanical Engineers-----a professional association) (National Fire Protection Association---a trade association) sets standards and makes recommendations.
They provide and advocate consensus codes and standards but have no legal authority. NFPA codes and standards are widely adopted and form part of US & State Laws.