Here's the question: why do they call it a tennis bracelet?
This answer is simple: because women's champ Chris Evert was wearing one in 1987's U.S. Open; the bracelet's clasp broke and the match was halted until the jewelry was retrieved. And the world looked at that bracelet and went, "Neat." So all thin strings of in-line diamonds in a regular pattern became known as tennis bracelets. Fair enough.
The corollary: why do tennis players wear so much jewelry? Every time I come across matches on the teevee, the women are wearing earrings, necklaces, and so on. Seems to me -- a former basketball player -- that putting something expensive and fragile on an athlete in play is kind of, well, silly. Possibly dangerous. I even looked up the ITF dress code from 2006 (the only one I could find online) to see what it said about jewelry -- most unhelpfully, there was nothing.
I remain puzzled.