What is it about US politics, that it seems obsessed with "hard working middle class families"?

I've nothing against people who fit into that category, but what about everyone else? What about hard-working working class and upper class families? Or hard working single people? Or people unemployed because their jobs have been outsourced to some 3rd world slave labour economy? Or widows/widowers? Or disabled people? Or mentally ill people? Or orphans? Or students? Or...? Or...? Or...?

Governments are supposed to be about supporting and representing all parts of society, whatever your background, whoever you voted for. This fiction that the US is entirely populated by poor, put-upon, over-taxed middle class families who never divorce, and are paying for a bunch of shirkers on benefits is just ludicrous. That this goes unquestioned in the press and TV says something deeply depressing about US society.