Because the people who invented it and who teach and revere its greatest writers speak it so much better than we do. Even casual chats with Brits on a street corner are full of wit and articulation.
I'm not talking about decyphering the regional accents or temporary idioms, but the compound sentences and verb tenses and sheer fluency of great English speakers. Listen to Margaret Thatcher to the UK House of Lords, Nigel Farage to the European Union parliament or Boris Johnson giving a talk about Western Civ, and feel bested.
“I’m not talking about decyphering the regional accents or temporary idioms”
I was.