All I'm saying is that almost everything in this game is a "cultural artifact". What makes the samurai any different?
Except you didn't say that. You snarked and asked a rhetorical question.
Socrates was a jerk.
Now, since here you asked an actual question that invites an answer, I will do my best to repond.
Yes, everything in D&D is a cultural artifact to one extent or another. However,
the best of those cultural artifacts are very high level and applicable to a myriad of situations. i.e. The originals-the fighting men and the magic users were meant to represent just about anyone who solved problems by force of arms or by magic respectively.
Of course, even waay back then, specific cultural interpretations started slipping in (the cleric) and by the Greyhawk supplement they were already falling hard for them (the paladin and druid). I can't do much about those, since they were considerably before my time, and
the years have worn the edges off of them--though to be fair, I'd probably remove them if I could.
To me, the best character classes are ones that can be turned to a myriad of interpretations in your campaign world; ie, the fighting man or the magic user. The more specific a concept, the less likely I can use it unmodified in my own games. There's a slippery slope of course. The Barbarian is a lot easier to generalize than the druid for instance. The ranger is a lot more subject to different interpretations than the paladin.
And then you come to things like the knight and the samurai. The knight is uncomfortable--I'd prefer Cavalier because, while it has a very specific cultural interpretation as a loyalist of King Charles' l, outside that very specific interpretation, it's a pretty general term for a heavily armed horse soldier (and it's been used in that fashion in D&D before), whereas knight presumes social station, and to an extent cultural background--though on a continental scale. To be fair, knights have been used to describe noble warriors of many cultures by English speaking peoples--so it's not a complete stretch to say it's a broad, fairly generic term. However, I think by using the term "knight", it makes it a lot harder to put aside the King Arthur trappings surrounding the name when you try to play in a campaign that doesn't include King Arthur trappings.
Everything said about the knight is about ten times more true for the samurai. It's a very specific term deriving from a specific time and place in a single country, that, incidentally, has never been used for anything else (even in cyberpunk-the term street samurai really only arises because of the assumption that Japan has taken everything over). And as such, it makes it really difficult to justify using "samurai" in a campaign world where Japan or a Japanese ersatz culture doesn't exist?.
I mean, look at those rules. Is there anything in either of those subclasses that don't fit a Primeval Thule campaign? No, not really, but in order to use them, the first thing everyone has to do is agree that samurai doesn't mean samurai and knight doesn't mean knight.
Do we have those problems with Champion or Battlemaster? I would submit that no we don't. Call the samurai the "Insightful Warrior" and then put in the flavor text that the inspiration for the class is the "legendary samurai" and now you've got a subclass that works in all sorts of campaigns without shoehorning and reflavoring.
As for Dungeons and Dragons...when I'm dm-ing, those things are whatever I say they are. When I'm playing, it's not up to me to decide what those things are--so no beef. But every time they tie fun mechanics to very specific cultural archetypes in the character creation rules
, they create a potential point of conflict between the player and DM.