Same as having to always mention the gender in English, ie "he said", whereas in Spanish it's just "said".
Also, if you don't know Spanish, I'm not going to teach it to you.
It's true it goes back to 1300, but it had also fallen out off fashion and was considered "wrong" later on. Languages change, and don't do so in a linear straight-forward way. From our perspective, it's very much a neologism (although it's been a few decades, and arguably already passed the neologism stage).
This is unlike, say, German, where each word has a random gender and you need to learn it along with the word. There, I agree, that's unnecessary overhead.