The history of Charm bracelets goes back as far as to the times of Egyptian Pharaohs. Also in those times people lived for a very short period of time (only for about 40 years), and while living much of the time they spent in preparations for their death. In previous times Charm bracelets first of all were considered to protect their owners from demon spirits, and they were worn for the sake of status, but also a Charm bracelet in those times was a sign for Gods to help them to put its wearer to an appropriate place after the person's death. And if we take for example the 20th century, we'll see that these Charm bracelets were given to young girls before they reach teenage years. And at every birthday or other important holiday a new charm or pendant was added to the bracelet. And it is from these times a pendant or a charm started to be just a nice little thing, usually reflecting hobbies or other interests of a child. It didn't have to be a birthday gemstone or something with some sense.
Now we have a broad variety of Charm bracelets made of various materials (silver, gold) and having various charms and pendants (hearts, flip-flops, etc).