And why do they not care? Because they don't know it in the firs place so it doesn't seem odd when guns are missing.
I think folks are taking their concepts and tropes from popular myth and fiction, not real-world history. Most folks don't seem to have any problem keeping them separate without cognitive dissonance.
I hang around with loads of people who do historical re-enactment (from Roman through Renaissance, and a couple Civil War folks as well), and outright historians. More historical knowledge than you can shake a stick at, well aware of when guns came into play. Not a one of them gives a whit that the historical gun is not available alongside the semi-historical armor.
I'm a physicist. I don't have any problems when Star Trek has holes in its science. I understand that it is fiction, and doesn't need to match the real world. That's okay with me.
When you would remove bows or lances from a fantasy game the players certainly would notice it.
Yes, but not because it is history, but because those are their fantasy tropes. In their minds, their anachronistic images of Robin Hood and the Knights of the Round Table are far more important than the technical bits of Agincourt.
The myth of King arthur plays out even before that in late roman times.
The myth of Arthur does not play out in one particular time, largely because it isn't really one myth. There's Geoffry of Monmouth's version, and Mallory's version. Then the Romantics got hold of it. Then there's T.H. White and Marion Zimmer Bradley and the movies Excalibur and First Knight, and many other versions. Some of these are entirely ambiguous about time periods. Some (like Peter David's) moves Arthur,
et al. into the modern era. All of those prior versions are in major part patched together out of stuff much older - Arthur's Grail grew out of older Celtic magical cauldrons, for example.
Saint George lived in the late 200s. Not 1200s, but 200s. Do a google image search on St. George and the Dragon. Many or most of the images you get have him in armor that most certainly didn't exist in 300. That's because he became a model for the chivalry. The myth has moved far away from the history (setting aside the complete lack of dragons in history).
Myths are not models of historical accuracy - they are
false stories. The popular ones are iconic, and tell us what we expect to appear in such fictions. If enough presenters show us Arthur or St. George in heavy plate with a lance, but no guns around, then the myth sits in some anachronistic version of reality. Which is fine, because these people weren't real anyway.
You want to impose your concept of technological consistency on your game, go to and have fun. You want to understand why others don't, you need to discard the idea that to do so is somehow natural.