Why do people wear rubber bands around their wrists.?

I have read some psychological studies where people will sometimes wear a rubberband around their wrist to help break a habit or a thought pattern that they wish to be rid of. For example, if a person swears and wants to break that habit, they may choose to wear a rubberband. Then, as soon as they slip up and cuss, they pull the band back and let go - it pops their wrist. The thought behind this is it's a kind of physical punishment for doing the thing you are trying to stop, and you begin to associate that small pain with the act of doing whatever it is you want to stop. To avoid the pain, you learn to stop doing the behavior. Of course, my daughter just likes to wear them so she can pull one off and shoot it at someone...