The "reason" in "for whatever reason" is that Samuelson is right, and most people saw that pretty quickly. Samuelson never returned to the question (he did write a later New Palgrave entry on it) because he had more productive things to do with his time. Samuelson wrote more than 300 papers on macroeconomics, trade, finance, money, everything.
Your final paragraph has a basic misunderstanding of the Cambridge capital controversy that is surprisingly common among the heterodox. There was a primitive theory of capital to which the CCC applied. But modelling improved, and this theory was completely superseded by the 70s. But somehow the heterodox have inflated it into being the core proposition of all of mainstream economics. The modern theory of capital is completely immune to the arguments of the CCC.
>But somehow the heterodox have inflated it into being the core proposition of all of mainstream economics.
My argument wasn't that neoclassical economics should be discounted as a result of CCC, but rather the grounds upon which it took place, where Marxian (well, labour accounting) economics took just as much of a hit as neoclassical economics did. My argument was that if your proposition is that the status of a discipline should be counted based on what transpired between 1960 and 1980, Marxian economics would only be as poor today as neoclassical economics was. Neoclassical economics improved its models, and Marxian economics either attempted to salvage an orthodox interpretation of Marx or to move on to other research projects (Analytical Marxism, Rational Choice Marxism) that do away with his "mystical shell".
I suppose when one thinks of trying to salvage Marx as trying to prove Fermat's Last Theorem (in fact, it is very much like that with the Fundamental Marxian Theorem), what Kliman et al. are doing given the models and notation set out by Samuelson and Leontief, or what Veneziani and Yoshihara are doing given neoclassical methods is a whole lot less objectionable. Neoclassical economics isn't dead because of Sraffa, and Marxian economics isn't dead because of the century-old presumption that Marx was an equilibrium theorist, or the presumption that he was a physicalist.
Your final paragraph has a basic misunderstanding of the Cambridge capital controversy that is surprisingly common among the heterodox. There was a primitive theory of capital to which the CCC applied. But modelling improved, and this theory was completely superseded by the 70s. But somehow the heterodox have inflated it into being the core proposition of all of mainstream economics. The modern theory of capital is completely immune to the arguments of the CCC.