We may smile for the camera today, but we didn't used to. In old photographs, people tended to not smile. While there are many explanations for this, the best explanation is related to culture and technology. Music by Electric Needle Room. https://www.electricneedleroom.us/

All images in the public domain or Matt owns the rights to.

To understand why people didn’t originally smile in photographs, you need to understand both the history of the photograph and a little art history as well. Before the photograph, the only way we knew what people or things looked like was by paintings. Some of these painters were masters at realistically depicting people. Realism (or naturalism) is the attempt to represent subject matter in art truthfully, and realism was particularly big in the 1800s. So, if someone is painted as they realistically looked, of course they usually would not be smiling. Imagine if you walked around everywhere smiling at all times. Not only is that not realistic, you might freak some people out. In fact, they might think you are little crazy. Most people spend most of their life neither smiling nor frowning. A smile is a response, not an expression, so it usually can’t be held for a long time.

By the 1600s, smiling in portraits was frowned upon. It was so taboo that only the poor, drunk, innocent, or children smiled in portraits. Basically, people believed that if you smiled in a portrait, you would be preserved in time and remembered in history as a fool. Because it was very expensive to get a portrait painted of yourself, most people rarely had the opportunity to get one, so when they did they wanted to be remembered as an idealized version of themselves, not as some jokester. When artists chose their subjects and painted them, they only tended to paint smiles for those who society already looked at as fools or childish. Thus, they were rare.