Bah, we have this in Greek also. How "cultured" one is can be seen in their speech. In Greek it's not speaking with big words ("exacerbate" vs. "make worse") but how many old Greek words one uses. For instance, pretentious twats that fancy themselves to be educated above the common folk will use words that sound like something Solon would have said to his slaves or Konstantine II to his horse.

Then there's the matter of diacritics. Hellenistic Greek used to have a panoply of diacritics, of two kinds, one kind to change the pitch of vowels and one to indicate a soft or hard sound (occasionally used on consontants, particularly rho, ρ). These could even be combined together to make Greek text something that looked a little like a vim regex. With time, Greek pronounciation lost its pitch accent and the diacritics became irrelevant to spoken Greek. Yet they were kept on in written text until the early 1980's when they were finally abolished from the school curriculum so most people today don't know how to use those. Unless of course they make a point of writing in the "polytonic" system that includes the diacritics, which they will invariably tell you is because "that's more correct". In truth, it's not more correct, it's anachronistic and archaic, but it marks the person out as someone who is e r u d i t e.

So it's not just English, sorry to say. In fact it's easier to see how you'd have classism in the UK, which is, after all, a United Kingdom, with a monarch and hereditary (?) lords and all. In a place like Greece it's harder to justify because there everyone is basically middle class, with small variations- and we booted our last king out in the 1970's. So here it's even more pathetic when people put on airs. In the UK it's more a political thing, they're trying to put you in your place. But in the UK, it's not the language that's the problem, it's that society is rigidly stratified and language is only the symptom of the awful inequalities.

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[1] Wikipedia has the works: https://en.wikipedia.org/wiki/Greek_diacritics

To be fair, once upon a time, England was full of English people. The educated would know Latin as that was the language of the church and of international correspondence. Then, the Normans arrived and the upper classes rapidly became somewhat French. So, the difference in speech between upper class and commoner as well as between educated and less educated (England had remarkably high literacy rates even among the commoners) has a strong historical basis. I also haven't even mentioned the influence of Danish (Viking) on the language. I would guess that part of the richness of the vocabulary is down to the fact that English is an amalgamation of several languages.