So why update the established ones? It damages the continuity (and credibility).
Except... The original objects would exist in the world (alongside any new ones they cared to create). Returning fans would recognize them (and the continuity effort); New fans would pick what they liked and see it all for the first time.
Exactly.
They didn't actually
need to make new weapons, they could have used the old ones and given them appropriate stats. I was overjoyed at first to see the Plasma Caster, as it was basically a rework of the original Plasma Rifle, but then I actually fired the thing...
I could understand it in FO3 to some extent, since it's set on the other side of the country, but even then there would still be some of the older weapons left, particularly in the sealed-off military bases dotting the landscape.