I discussed this question with a Englishman a few years ago. He didn't believe that British singers did this, although it seemed obvious to me.
I think there are several possible reasons for articulating with an American accent when singing; the most obvious reason being the traditional influence that American singers have had on British music culture. Each generation is influenced by the previous, so we Brits are influenced by the Yanks. Another possible reason could be marketing. Historically, the US market has been a gold mine for British artists - the potential income from the US was far greater than what could be achieved from the domestic UK market.
Iain |