Why didn't Queen Victoria smile in photos?

Early Photography required long exposure times, so the subject needed to hold a pose for a minute or more (ever make a pin-point camera in high school?). Any shift of expression would result in a blurred, ruined image. A stern or reposed expression is much easier to maintain than a true, or even a fake smile. When exposure times improved in the 20th century, we all began to say "Cheese".