Signifiers of youth.  Hams destroy them by being fat, so they have to artificially add new ones.  So they become goths.  There's not a lot of old goths.  Being goth is a visual cue that says "I'm young and rebellious and possibly averse to giving a shit what you think".  So it's like they're also preemptively shrugging off criticism for being fat.  That's my theory anyway.