For track, Ohio has a "no jewelery rule" in middle school and high school. This rule appears to go away later on (college, pros).
I've got the parents of young kids who will be in the summer track program I work with asking me why, (we have that same rule just to get the kids ready for the rules down the road). My answer is always "because that's the rule in MS and HS. But, I'm not really sure why the rule is there for them.
So, what's the deal? Just so a kid doesn't rip an earlobe?