Dutch linguistic purism

One of the great annoyances about the Dutch language, is that the definition of the 'correct' standard languages is rather different from what we actually speak. This has to do with the standardisation of the Dutch language when the first bible translation was introduced. Dutch was morphed into some sort of mixture between Latin and Dutch, giving rise to new case forms and constructions previously unheard of in Dutch.

By now making a distinction between masculine and feminine is finally on its way out; and writing cases has been abolished for some time too. Nevertheless some things persist. Some people insist on making a difference between a dative and accusative third person pronoun hun and hen (I'm not even sure which of the two is which), which were originally just two dialectal variants of the same word. But were taken to be used as two different cases to facilitate a more accurate representation of the Greek language.

Another truly, and even, far more common 'correction' that is made to people's speech is the comparative.

In English we would write the following sentence:
He doesn't have more children than me.

'than me'; perfectly normal to use 'me' here, which is what all other germanic language do, except for 'correct' Dutch. We're supposed to say:

Hij heeft niet meer kinderen dan ik.

IK, nominative! Why? Because apparently you're supposed to fill in the rest of the sentence as follows:

Hij heeft niet meer kinderen dan ik heb.
or in English: He doesn't have more children than I have.

But English has no problem changing pronominal case here, why should we? And then when we look at actual spoken dutch we indeed find:

Hij heeft niet meer kinderen dan mij. As we would expect it. I had a previous suspicion that this must have been a early-modern dutch prescriptivist innovation, and as it turns out, I'm right. In Middle Dutch texts we find this sentence written in 1200 AD:

Hine hadde niet meer kinder dan mi
He-NEG had NEG more children than me.

So, the 'dan ik' construction is historically wrong. This never seems to convince prescriptivists though. Even if the construction wasn't historically wrong though. Why would anyone say that something that 90% of the population says is 'incorrect'. By which standard are you measuring language? Isn't language defined by the people who speak it? If it isn't, then what does tell us what language is? Because clearly language itself can't be used since it has no authority over what language is according to these prescriptivists. Do they really think grammar books come falling from the sky through some divine intervention?

There's an enormous contradiction here. I believe language should be spoken the way it is spoken, not the way some 17th century theologist would like to see us speak some pseudo-latin-dutch hybrid monster.