Why does Whitman describe Americans from different social classes and professions in "Song of Myself"?

He described Americans from various social classes and professions in order to develop his ideas of democracy and equality.

His poem, Song of Myself, celebrates his own being, as well as other people's. He wanted to include as many social classes as possible so as to show how people are equal no matter which social class they belong to, or job they have - they are all people, and by extension, equal.