I think Mr. Friedman, like a lot of Libertarians, likes simplicity. There should be a handful of axioms from which all morality can be derived, allowing all actions to evaluated by a nice simple single-dimensional metric.
The fact that a well-run company has dozens of different obligations from financial to ethical, many often running counter to each other makes it hard to rigorously state “this is the way a company should be run.” As soon as you allow judgement into the mix, complexity and ambiguity overwhelm the beautiful, elegant simplicity and certainty that I have found many Libertarians crave.
Shareholder value is, in my opinion, a classical example of that desire for simplicity.
(I will say that I am not as convinced that it has made a major difference in corporate governance. Neither private companies nor companies of old seem less devoted to the ills ascribed to “shareholder value”. Likewise, good companies seem to exist at about the same ratio in both private and public companies.)
