Because president Franklin D. Roosevelt was very passionate about preserving America and through the Great Depression he wanted to help build America up so when they came out of it they had something to be proud of. And it also created work because at the time it was scarce. The artist created stuff to basically distract and keep the country up and to document and preserve America’s history. Because it showed how even at their lowest they could worked thru it to build American up.
Sorry if that’s not what your looking for I haven’t studied president Franklin D. Roosevelt in a while!:)