The absence of an academy does not stop there being many prescriptivists. Nor do many of these refer to descriptive accuracy- I was merely stating what they are not supporting their views. In an extreme case, those who claim that the correct form is 'it is I' are not making any reference whatsoever to a description, but simply applying their understanding of a rule, one they believe carries greater authority that the vast majority of native users. I was not upholding their vews, just describing them.
Unless some grammarian has a direct line to the god of language, prescriptive 'rules' can only be based on descriptive research on usage – though such research will always unfinished. And prescriptivist rules are no more than analytical constructs – at best