Has anyone read the Black Library book Horus Rising, which is set 10,000 years before the current 40k timeframe?
There is an interesting bit of dialogue from the then good guy Abbadon, just after one of the ‘Space Marines bonding Top Gun style’ bits. The future scourge of mankind tells one of his battle brothers, and I quote:
\"Helmets, that’s where true power lies in this galaxy. Not in the bark of a bolter round, the devastating hammer blow of an orbital bombardment or the stern will and resolve of an entire Marine Chapter, but in the possession of many pretty shiny helmets. Oh I just love them, they are so super! Only when I have more helmets than I can possibly carry will I be satisfied, and I want all the varieties and colours under the sun too. I have a wing of the Adeptus Mechanicus working on an advanced helmet removal tool to aid me in my gathering. They even made a helmet storage rack for the top of my armour. It’s a little impractical, spiky as hell, rather dark and twisted looking and perforates the helmets like you wouldn’t believe but I wear it anyway from time to time... You know, just to keep them happy, they put in so much effort.
“The problem is that the Emperor doesn’t really share my views on helmets. I dunno, he seems to think we can rule with oppression and fear, throw our weight around a bit... I think more helmets is the way forward. Let’s just get lots and lots of helmets.
“I’m going to suggest a change of policy to him when we next meet. More helmets for all. In the far future, perhaps the 41st millennium, I foresee that there will be only helmets.
“You’re all with me right men?”
At this point they all respond with a hearty cheer and polish their helmets together. Quite an illuminating little passage I’m sure you will agree.