Why is simply standing up so good for us?

I first began to suspect standing was beneficial when I saw singer Tony Bennett interviewed on Howard Stern. Bennett is in his eighties and , when he arrived, Howard showed him a chair and he said , “that’s ok; I’ll stand.” And he stood for half an hour.
Do you know why standing is good or do you deny the usefulness of standing? http://www.aitse.org/achieving-longevity-by-standing-up/