Keep in mind that the Web standard eventually became prescriptive because descriptive standards failed to catch up. Likewise it can be argued that descriptive standards for the common OS interface are no longer usable.
To be crass, description is only useful for existing things and prescription hinders making innovative things. I think social forces make it natural that standards are treated both descriptively and prescriptively, and that too leads to angst. Case in point, POSIX was once more descriptive, but then people wanted backwards compatibility for existing and new OSes, which made it more prescriptive. The takeaway is that ad-hoc things become permanent once they are too difficult to remove, and then people are sad. Nothing is immune, so just make reasonable attempts for the standard and the culture to harmonize for a specific purpose.
