Well at some point during the 60's muggings stopped happening and novelty crimes become huge. Since they all run together a bit even batman needed to take trophies to remind himself which kind of becostumed tosspot he was dealing with this week. "Is this two face, no face, po face or O face?".
Also, as a minor side point to the current superhero pontificating, why is it always the heros that get the blame for criminals going loose? I mean surely the justice and prison services must hold some culpability for all of it.