The answer is both an economic and environmental one. Economically speaking, there was a market which existed for affordable pearls, and therefore a way was found in order to serve that market. This was accomplished environmentally, as man discovered that he could “assist” in pearl production, resulting in more pearls, and lower prices, for everyone.
Prior to the last century or so, pearl ownership was restricted to the rich and royalty. Mother Nature was (and is) fickle, and so pearl farmers had to wait for her to produce pearls at her leisure. This resulted in low pearl numbers worldwide, making it a very expensive gemstone.
But humans discovered that they could intervene into the production process, increasing the likelihood that pearls would be produced and greatly expanding the number of pearls available for purchase. Rather than waiting for an irritant to enter a pearl, farmers discovered that they could insert the irritant themselves and then simply wait for the oyster to work its magic.
This discovery revolutionized the pearl industry, as post- World War families in America and around the globe now found themselves able to afford the previously-unobtainable gem. The result was a booming pearl market which has continued to this day.
Modern day pearl production is a wonderful example of human innovation and nature working hand in hand. If you love your pearls, you should be thankful that the pearl farmers of the past refused to believe that pearl ownership should be limited to the wealthy.