Because it explains how the lemons and oranges that are delivered to his back door are all used up within a fortnight because he is always throwing parties and events. It also explains that tons of caterers come down with canvas to decorate his enormous garden.
Poe uses rhyme to create a nostalgic mood. Most of Poes works are dark and mysterious. There are a few that are nostalgic, so based upon this, Im going with nostalgia.
