You need some warmth or levity in a bleak setting such as Megacity One. This is often seen in the form of the Fatties who are some of the kindest and most compassionate of the citizens.
The great thing about Dredd is that he doesn’t need to be the star of every story. The setting is so well realised that it stands strong without him, or at least with him as supporting cast. And we see a rare moment of kindness, or at least politeness from old stony-face.