Whether the linguistics experts like it or not, there remains an idea of ‘standard English’ as it is spoken in Britain; there are different but related standards in other countries where English is the principal or a principal language, notably in America, but also in Australia, India and the Far East. These standards are set by an educated class within those communities: and those who wish to be included, or to consider themselves included, in that class must subscribe to the rules.
Standard English is also a measure that certain of us impose upon others — those applying for a job, for example, or seeking other favours. It is a fact that people are judged by how they speak and write, however offensive or unfair that may seem to some. This is partly the legacy of a popular grammatical movement in the late nineteenth and early twentieth centuries whose textbooks remain on the shelves of many professional writers to this day. It is also because of the British trait of looking down upon people whom we consider less educated than we are: for a grammatically precise command of English and an ability to choose words correctly have long been considered by many to be the mark of an educated person. Millions of English speakers believe there is such a thing as good English, and aspire to write it and speak it. Few Britons in recent decades will have learnt the standard in schools. As a result, they cannot use the precision tool of our language to its full capabilities.