Why do some of the tea dragons have jewelry and others don't?
The same reason people do! fashion~
More lengthy answer: some Tea Dragons will take a deep liking to certain trinkets that their owners might find (or present them with). You can’t persuade a Tea Dragon to wear something it doesn’t want to, and likewise it’s very difficult to persuade them not to wear something they have become very taken with. They’re sort of like teenaged cats.