Some of them are more useful than forged counterparts.
The Helswath still has more MT than a Tomohawk after forging and gives a Defense bonus, although it will have less Hit if the Tomohawk is forged to have more Hit.
Ragnell is the only physical ranged sword that all sword classes can use, also gives a Defense boost.
Gradivus outclasses the Spear in just about every way and can also be used as an Elixir.
Valflame's 21 might is better than any Tome you can Forge, and the Book of Naga gives Defense Boosts you can't get from any other tome.
Yewfelle's speed boost is nice, and Double Bow's 3 range could be useful in certain situations.
In most cases I'll agree that Forges end up being a bit better (especially with Braves). Gradivus and Ragnell are probably the best of the bunch, since Brave Weapons only give you 1-range. There might be a few others that I missed.