To me, the importance of this sort of Standard English is that it serves as something of a lingua franca for people around the world.
There are, of course, many variations on English since it is spoken in so many countries. However, there is generally a "correct" English that is taught that is based on the "Queen's English." Because this standard version has come to be taught worldwide, it is very important today.
I disagree somewhat with the previous post. The 'King's English' isn't the lingua franca today. I feel that American English has very much taken it's place. the book 'The King's English' was published in 1906 and written by the Fowler brothers. It detailed things such as the correct usage of shall and will. Unfortunately , in my opinion , much of this correct usage has disappeared and is no longer in common use.