There is a very funny moment in the third season of Rowan Atkinson's hit sitcom " Blackadder" in which Dr. Johnson, the real-life historical figure who wrote what (he claimed) was the first comprehensive English language dictionary, tries to explain to the idiotic Prince Regent that it is a book about what English words mean. Prince George replies, "But I know what English words mean!" dismissing years of the good doctor's hard work. Johnson is outraged and the prince's potential patronage is thrown into question.
As stupid as the prince character is, a lot of people do seem to agree with him, that they know what English words mean thus don't need a book about it. However, Johnson was working at a time that the mere idea of English as an elevated, international language was considered silly. The British Empire was just starting up, Shakespeare's work was only 200 years old, and John Milton's "Paradise Lost" - which was written to put English on the map alongside that previous global lingua franca of Latin - hadn't turned 100 yet.
These days, English is the international language of choice; most internet traffic is written in it, and it outstrips Mandarin Chinese in the number of speakers worldwide. Everyone takes it seriously - and knowing a lot of its 200,000 words is simply part of being an educated person. How well do you know not just the language but the vocabulary of Shakespeare?