I think beach nourishment is used to help sell housing projects and protect the towns' tax base. People have this idea of the Outer Banks as a wild, wind-swept destination and an artificial beach will take away that lure which in turn could hurt the economy.
If you widen a beach, then yes, you will reduce impact from certain storms. But take a big hurricane, something like Katrina, and there's no artificial beach we know of that would've prevented that kind of destruction. That did nothing.