When shooting for stock photo agencies or news media it is important to have a huge selection of photographs. Each photograph should be powerful and unique. Art directors and photo editors have to choose between millions of opportunities and they typically will try many and then narrow the selection down to a dozen finalists and allow a team or focus group to provide input / including clients before the final selection is made. Many photographers start relationships with national accounts by taking photographs as a hobby and then submitting them for stock use until they develop enough relationships to start a full time career out of photography. I both modeled for photographers from the Corbis Stock Market (Microsoft owned now) and shot ads for FORD and other fortune 100 companies by submitting thousands of photographs for stock.