Perhaps simply because it is called "Githyanki Half Plate" opposed to simply "half plate". Other armors in the game are not racially designated and considering the attitude the Gith in game have toward all of the "lower" races, I agree with the OP they might have questions about non-Gith running around in Gith armor.
Call them French Fries. That doesn't mean France is going to start cutting throats at Mickey D's.
It's just crap logic that's filled with presumption. Because that's the way "you imagine it being" doesn't mean it's that way.
It's easy to say Githyanki wouldn't suffer someone else wearing "their" armor. It takes a bit more nuance to consider other possibilities.
Are you kidding? Githyanki are VERY proud and arrogant people. If a Gith finds out you're wearing Gith armor, the assumption should be that you killed a Gith and stole their armor. That would be the equivalent of a Mandalorian catching a non Mando in their armor. Kill on sight!
Oh, good grief, here we go again with the armchair expertise.
To reiterate: for all you know the Githyanki sell the armor at an astral marketplace. But instead of considering anything outside the box of your current head canon, you literally say that the immediate assumption *should* be that a Gith was killed and the armor was stolen.
We've all been DMs, you know. It's not an earned title. In my experience, the best DMs are usually the ones who think things through and come to interesting, out-of-the-box conclusions about things, as opposed to ones who jump on the bandwagon of the most obvious, arbitrary, and unbendable idea.
I accept that Githyanki hunt down Silver Swords if they are in the possession of non-Githyanki. That's canon. That's accepted.
The insistence that they also hunt down their mundane, non-magical half plate is not canon. It's not accepted.
