One of the reasons men and women accessorize their getup is to be able to shout to the world that “hey, this is my style, I like this because it makes me feel good.” Another reason is to be able to follow what their “idols” are wearing as if to say, “hey, I am a fan of so and so that is why I am wearing what he or she is wearing!”
Accessorizing is part of dressing up. It makes one’s whole getup more interesting as details are clipped or hung or worn. Fashion jewelry are sold everywhere because there simply is a market for such. If you go to the malls in the Philippines like SM, for example, you will find a certain location where all stalls are setup side by side selling almost the same things the others are selling. That is what you call competition and the vendors don’t seem to mind since all of them seem to have sales for the day. With so many people lurking around, impulse buyers are easy targets.
Men are no different. They have their own stuff for fashion. It used to be that necklaces are only worn by women. This generation seem to be saying that men ought to have fashion say as well. Caps, rings, earrings (even several of them per ear), nose rings, belly button piercings, anklets, watches, bracelets, are ways to tell the world what define these men. Check this link for more details.
As the generation passes by, there will be another set of youths that will define what they wanted to look like. Fashion, though, is a cycle. Since the people of older generations have something to say about what they were back then, some pick up the idea and find that it is cool.