Languages evolve or devolve until they reach the state of minimum energy consumption necessary for its speakers to conduct their affairs.
Low IQ descendants of speakers of English will quickly lose most of their vocabulary and complex grammatical structures if they end up on an isolated island for generations. While the complexity of the language will increase if there is a general rise in IQ as the population of speakers is held steady or increases.
The way of speaking of the upper class seems unnecessarily complicated and pretentious to the average person. Some of the upper class do make their speech more complex to show off and differentiate themselves from those below them, but since the upper class has a higher IQ than the lower classes, their speech will always be more complex.
Some people who are desperate to enter the upper class, or who are already there and have nothing better to do with their sad lives, go out of their way to use rare and unnecessarily complex words and structures to impress others with similarly sad lives, because it is apparently a mark of intelligence to use ten words when five would do.
An actually good and intelligent writer (like George Orwell) will use the minimum number of words necessary, and the simplest available, to express their ideas. The writing’s complexity only increases when the ideas demand it. Complexity is never used when simplicity would do just as well. While a pretentious writer, like so many philosophy professors, will use a thousand words when a single sentence would do.