Jesus that's a LOT of threads at once over the same subject, lol.
But @ thread, there's two different answers to this:
Actual reason: it was the first game and they were still sorting out how things would go and didn't feel the need to add that.
In-universe reason: he had no idea he could do that. Even when he does dual wield in 2 he needed a special form for it (although that was mostly gameplay and didn't really reflect on the story-side of it.). In 3 he was more experient so that's probably the justification for it lol