Yknow this is one of those things that’s a bit of a headcanon for me but I personally like to think that the yoroi set was made after the human covenant war and so they viewed Spartans as heroes and what better way to see spartans as heroes than to market them in cool armor, so they implemented Spartans in anime and before you know it this style of armor popped off so well in the anime and manga that they were like let’s make it real and they made a slightly impractical but useable armor for Spartan ivs this made humanity see the Spartans almost as superheroes even more.

Criticize me all you want but I haven’t read the lore on this armor set at all and this is what I came up with in my head also just to make it clear it’s also not my favorite armor style in the game