Our speaker manages to maintain a bit of distance from her subjects – she's not the sort to pry into their private lies, giving us all the juicy details of their scandals and sorrows in order to draw us into her poem. Nope, this speaker doesn't even give us her subjects' names.
Instead, she creates something like a snapshot of the space in which these two people move and live, sketching out their forms as they sit down together to share a cheap dinner. Besides a few moments when the poem's speaker starts to channel society's general impressions of this couple, she remains pretty aloof. She'll describe the things that cluster around their room, that anyone can spot, but she won't enter into their hearts and minds.
Why? Well, that's a good question. We're guessing that this level of anonymity allows the speaker to seem impartial, making it easier for Brooks to level some rather devastating social observations in a casual (and even off-handed) tone. Brooks was pretty careful to craft an utterly unavailable speaker – which turns out to be a rather good thing.