In my opinion, the reason for this is the interaction that most operators have with senior NCOs, and more specifically the interaction that most senior NCOs have with operators. Look at the command structure in most wings - your highest officers are the DOs, deputy commanders, and commanders, and your highest NCOs are generally first shirts, superintendents, and command Chiefs. By the nature of their job, the enlisted leadership do not deal with officers, but unfortunately from my experience until the last couple years it also tends to mean they don't interact with them. My entire flying career the only NCOs I dealt with on a working level were the NCOICs of SARM/HARM and life support. Until I was a major I was addressed directly by E-9s only twice; once for acknowledging but not returning an airmen's salute on the flightline (because it's no salute and my gear was in my right hand), and once for having my flight suit sleeves pushed up.
In my last two assignments that has changed significantly, but I put that more specifically on the senior enlisted personnel in those two assignments. The first shirts and chiefs actually get out among the populace to interact rather than solely being a reactive entity and only dealing with enlisted personnel.
So when someone's only interaction with an E-9 is him acting as a uniform nazi, it is understandable why they have that impression.