Nadaraya-Watson vs Lagrange Interpolation

Ok, I don't get it, what do Nadaraya-Watson estimators have over Lagrange Interpolation?
Since the choice of Kernel doesn't matter much, you can just set k(u)=u, right..?
What am I not getting here?
(Kernel methods involve Convolution Smoothing)
                - = - Vasos-Peter John Panagiotopoulos II, Columbia'81+, Bio$trategist ---{Nothing herein constitutes advice. Everything fully disclaimed.}---
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