Two words: selection and price.
The Caribbean island jewelers offer a larger selection of jewelry, diamonds gemstones, and watches than any other region of the world. Walk into your local jeweler in the US and ask to see their Tanzanite or Emerald rings. They may have a few. In the Caribbean you will see hundreds of them. The more choices you have, the better chance you’ll find that special treasure you’ve only dreamed of.
Many manufacturers available in the islands are not found in the United States so this is your chance to take home a special gemstone or jewelry design that no one else will own. And even better, they are all available at duty free prices so you will save by buying in the Caribbean. By not having to pay the sales taxes imposed in the US many a smart shopper has paid for their Caribbean vacation.