Tradition is not always a good thing. The turned-down eyes on hooks and the Turle knot were invented specifically for gut leaders. Gut required a knot that didn't crimp down on itself (like a clinch knot does) but the Turle made the fly ride "cocked" when tied to a straight-eyed hook. So hook makers started turning down the eyes so the Turle knot and gut leader gave a straight pull.
Monofilimant line came along, but hook makers are STILL making fly hooks with turned-down eyes. Even though nobody has used a gut leader in more than seven decades. There's absolutely no need for turned-down fly hooks today, but...
Well, it's tradition.
