The language of operas

Should operas be performed in the language of their composers? 'When Giuseppe Verdi's Don Carlos premiered in Paris, it was performed in French, but for its Italian premiere Verdi revised it and it was performed in Italian. For many years Wagner's operas, when performed in Italy, were sung in Italian with Wagner's blessing... Composers have always wanted their work to be performed in the language that most of the audience speaks. It would then seem logical that every opera company in the world would adhere to the composer's wishes and perform their masterpieces in the language of the people who make up the audience. However, not one major opera company in the world does this.Why not?' More... (Via)