I've been thinking about the dark ages, when Latin was replaced by the demotic across Europe. For a long time educated and literate people continued to converse with each other in Latin. Sorry, you know all this, I'm just setting a context. I read some article for instance saying that most of early French was just a drawled form of Latin and army-slang. So 'diurnal' became 'journal'.
It seems to me that 'journal' is much more like 'diurnal' than the language spoken in the Wire is like Standard English.
It seems as if our diverse languages are held together by a conventional Standard Form, which is based on written English, and functions a bit like Latin in the dark ages.
For instance, in The Wire most people pronounce 'All right' as a long-drawn out 'ite', a bit like 'Ah-eet', but not really two syllables. Whereas I pronounce it more like 'Orr-eye' with a 't' at the end which is formed by my tongue but isn't voiced. Some Londoners say something more like 'Auw-oyy' with the w and y sounds quite hard. These are really different languages.
In 'The Name of the Rose' they are amazed that Dante has written a poem in Italian instead of Latin. And we think - of course poetry is written in the demotic. But poetry is usually written in Standard English, which isn't our demotic. Very occasionally someone writes in a phonetic rendition of colloquial speech, but that is felt to be a bit quirky.
I'm also thinking of written Chinese which ties together the very different spoken languages.
People often think global communications will homogenise language, but I'm not that it will. And perhaps we all speak multiple languages without realising it, because we don't label them as such.