For the life of me, I can't figure out why. But I'll take a stab at it.
You'll see many of the Boston Red Sox sporting the necklaces when they host the Tampa Bay Rays today in a pivotal Game 3 matchup at Fenway Park.
Phiten necklaces are designed to relieve neck and shoulder pain while looking awesome around your neck when you blast a two-run homer.
About.com's Scott Kendrick weighs in on the accessory here.