Date: 12-24-10 07:41
I was always told that the King stood.. because he couldn't sit any longer, and if the King was standing, everyone stood. Thus, the tradition began. Time for some research!
History claims that during the first performance of Handel’s "Messiah" in London, King George II was in attendance. When the first strains of "Hallelujah" began, the king was so moved that he rose to his feet, and, following royal protocol, all others in attendance were compelled to do the same. It is unknown whether the king was simply enthralled by the music itself, or whether he was showing subjection and deference to Christ as the “king of kings and lord of lords,” as the text goes.
Regardless of why King George II stood, he did, and people the world over have done the same ever since.