So there's 2 separate lines of thought going on in this thread.
OP wants it so armour simply looks different based on your race.
Commenters are thinking about having racially (And gender) locked armour.
As far as both of these goes...
Armour having a different appearance depending on who wears it is kind of weird. Especially if it's a specific item. Like, say one of the Adamantine armours made in Grymforge with the same design as Grym. It'd make no sense for that armor to come out with elvish flare just because Astarion is wearing it instead of a Duergar PC.
Even for the mundane items you'd expect them to be stylized based how the person who made it designed it (Which does in fact open up the potential for having items with unique looks from different vendors. Such as Dammon making tiefling/infernal engine style items, while say Greymon will sell things made by Duergar with their style to it)
Of course, the issue with such things also includes the extra work it would require to make more unique appearances for things (With it being rendered moot for most mundane items anyway because of how quickly you end up clad in magical items that outperform basic stuff)
As for having racial locked items, it'd be a bit much to have all items function like that (Especially if you can just hand-wave and say it fits "Because Magic" even for mundane items). But having a few more racial specific magic items would be neat. There's already a few things that provide a benefit for certain races (Like several items that deal bonus Psychic damage for Githyanki, a rapier that deals extra poison damage for Drow, gloves that provide extra Dex for Halflings/Gnomes and a thrown hammer that deals bonus damage for Dwarves)
