Whether or not one believes there is any metaphysical significance to the birthstones, we can't deny the strategic power it wields for jewelry-makers. When a customer sees a ring display of a dozen or so colors in the same style, she's already accustomed to expect that one in the display is her birthstone, and thus will immediately look for "her" stone. Additionally, a very popular gift for women is a "Mother's" or "Grandmother's" ring or pendant, which uses the birthstones of her children and grandchildren in a personalized jewelry design. If you can create rings or pendants in an assortment of stones, such as a multiple-bead or multiple-CZ ring, you will be very popular leading up to May for Mother's Day!
Tradition has it that the birthstones originated with the High Priest Aaron's breastplate as described in the Bible, and was standardized into 12 recommended by Tiffany & Co in this Tiffany-sponsored poem dating to 1870. Other cultures, including the Babylonians and the Tibetans, had separate birthstones, as well as ancient Indian or Ayurvedic birthstones.