Then perhaps it's something that might be confined to silly young subalterns and older officers who should know better? Certainly the Great War taught many officers that a rifle was far more useful and far less noticeable, as did the Boer War a decade before. I've no doubt that fighting officers on the NWF would have discovered the same. There would no doubt be some very short careers for those who chose not to dive for cover when the shooting started, so as not to create the wrong impression to the men, and probably also for those who chose to look 'like an officer' should.
I don't know where Mad Jack did his early soldiering, but his comments about an officer being improperly dressed without a sword, imply there were some who put appearance over practicality. For my part, I'd go with a rifle too.